Question: Howdy, I’m asking about my Lord Baltimore hibiscus. It’s overall healthy and blooming well. But this season, I’ve have had numerous brown leaf spots then eventually leaf yellows and spots turn darker. Now I’m noticing that some flower buds are yellowing and dying out before bloom. It also has banded-wing whitefles with eggs underneath a lot of leaves as well but that’s pretty normal. Not sure if the two are related though. I have treated a couple of times with Neem oil and once with the Bayer Advanced Fungicide/Miticide spray but it hasn’t slowed it down yet. Any other advice you might give?
Answer: Lord Baltimore hibiscus (Hibiscus moscheutos), also known as Rose Mallow, is a shrub with huge, beautiful red flowers. It is native to wet, marshy areas in the southeastern United States. They bloom from August to October with multiple flowers per plant, each flower lasting only 1 day.
I suspect your plant may be suffering from several issues:
Thrips are a tiny, slender insect with fringed wings. They are likely eating on and damaging the buds at a young age. To control thrips, apply a contact insecticide every 7 to 14 days, thoroughly covering the buds, shoot tips, and any other areas showing damage. Organic options include insecticides with active ingredients azadirachtin, insecticidal soaps, horticultural oil, neem oil, and pyrethrins. Spinosad is more effective than these. Mix it with horticultural oil to increase its persistence within the plant tissue. This link from the University of California provides more information on thrips: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7429.html
Hibiscus moscheutos requires wet to consistently moist soil to thrive. Your plant may be suffering from leaf scorch if the soil is drying out between waterings. Inadequate moisture can result in scorch symptoms on foliage, stunting, leaf yellowing, leaf drop, and flower bud death before bloom.
You could also have a fungal issue. In all cases of plant diseases, practicing good sanitation is important to avoid spread:
- Pick up and discard any plant debris and remove infected leaves, do not compost these.
- Clean tools used to prune diseased plants with a weak solution of bleach, rubbing alcohol, or a disinfectant.
- Don’t let mulch touch the stem to prevent Southern stem blight.
Treat with a fungicide at the first sign of the disease following the label directions for the first and subsequent applications. Please carefully read the label to be sure it’s suitable for hardy hibiscus, and carefully follow the application directions and safety precautions. This factsheet from the University of Florida lists fungicides that are suitable for ornamental plants: http://edis.ifas.ufl.edu/pdffiles/pg/pg08900.pdf
This website from North Carolina University has more info about Hibiscus moscheutos: https://plants.ces.ncsu.edu/plants/hibiscus-moscheutos/. This website from Clemson University has more general information about hibiscus: https://hgic.clemson.edu/factsheet/hibiscus/
Frequently Asked Question Categories
- Flowering Perennials
- Trees and Shrubs
- Water Conservation
- Insects, Diseases and Pests
Question: I have a section of my front yard that started getting grass burs a few summers ago. I have pulled them, overseeded, everything I can think of with the exception of killing the grass, and nothing gets rid of them. I am all organic and we do over-seed with ryegrass in the winter. I use Bermuda grass in the front yard and that section of the yard gets 8 hours of sun. I feel like that section of grass is just unhealthy. Will anything make them go away and never come back?
Answer: Grassbur, also known as field sandbur (Cenchrus spinifex), is a summer annual grassy weed that grows in all types of soils and can be found in just about everywhere grass is growing: residential lawns, sports fields, parks and along roadsides. Grassbur has sharp, spiny burs that are part of their flower clusters. These burs seem to stick to and in everything and can be painful. It has a very long growing season, germinating in late spring and continuing to grow until the first killing frost in fall. It is a particularly pesky weed because they produce a lot of seeds that can lay dormant for a year or more before germinating. Because of this, grassbur cannot be eradicated in one season.
According to Texas A&M AgriLife Extension and University of Missouri Extension, here are the steps to controlling grassbur:
- Apply a pre-emergence herbicide between March 15 and April 1.
- In the case of heavy infestations, re-apply a pre-emergence herbicide every 6 weeksthrough September.
- Look for a pre-emergence herbicide labeled for sandbur control with one of these active ingredients: Pendimethalin, Benefin/Oryzalin, or Oryzalin. Pre-emergence herbicides must be watered in thoroughly to be effective. So, plan to apply just before a high probability of rain or irrigate the area after application.
- Note that pre-emergence herbicides inhibit the germination of grass seeds so follow the directions on the label for the timing of application if you plan to reseed your lawn.
- If you have grassbur germinate despite the application of a pre-emergence herbicide, spot treat with a post-emergence herbicide with the active ingredient MSMA or Fenoxaprop-ethyl. The post-emergence herbicide needs to be applied as a spray when the plants are young. Apply on a calm day, and carefully apply to the grassbur plants only to avoid killing your Bermuda grass. Tip: Make a shield around the nozzle of the sprayer by taping the cutoff top of a plastic soda bottle or milk jug around the nozzle.
- These steps will need to be repeated for several seasons to completely eradicate the grassbur seeds.
Click these links to read more about controlling grassbur: https://extension.missouri.edu/scott/documents/Ag/Quick-Reference-Guides/Field-Sandbur-Control-for-Lawns.pdf and https://aggie-horticulture.tamu.edu/plantanswers/turf/grassbur.html
Organic and cultural controls include:
- Setting your mower blade to a low height, mow and bag the seed heads (burs) and discard them in the trash. This will need to be done every mowing through September for several seasons.
- According to the University of Hawaii, grassy weeds are particularly difficult to control organically. They recommend applying organic herbicides with active ingredients clove oil (eugenol), citric acid, and acetic acid to very young plants, thoroughly coating the leaves on hot, dry days. (Source website: https://www.ctahr.hawaii.edu/UHMG/downloads/Organic_weed_HG.pdf)
- Although not scientifically proven, some gardeners use corn gluten meal as an organic pre-emergence. Although, a study by North Carolina State University Extension indicated that corn gluten meal was not very effective as a pre-emergence herbicide for field sandburs. (Source website: https://ucanr.edu/sites/Grown_in_Marin/files/275912.pdf)
As with any chemical applied in the landscape, either organic or inorganic, read the label carefully for the suitability, directions for use, and follow all safety precautions.
The best defense for grassbur and other lawn weeds is a healthy lawn. It would be helpful to have a soil analysis done. The analysis will help you understand what nutrients your soil needs to grow healthy turf. Click on this link to learn about soil testing and the steps to have one completed: https://dcmga.com/north-texas-gardening/community-gardening/soil-testing/.
Question: My lawn is suffering, even though I follow Texas A&M guidelines on irrigation and fertilization. The turf gets 6 hours of sun daily. Would core aeration help?
Answer: Core aeration involves removing plugs of soil from a landscape troubled by heavy, clay soil and/or compaction from foot traffic or construction. Turf needs oxygen as much as it needs water, so periodic core aeration advances the absorption of both elements. Topdressing with compost afterward further improves soil by adding microbes and nutrients to grow healthy roots, to discourage suffocating thatch, and to improve water infiltration.
To determine if your lawn would benefit from aeration, do a screwdriver test. Probe the suspect areas with a screwdriver; if you can’t easily penetrate the earth, you’ve got compacted soil and aeration will be beneficial.
Texas A&M recommends twice yearly core aeration of the most compacted areas of your lawn. This task should be done in the cool of the day during times of active turf growth, not during dormancy. (March and October) Soil needs to be somewhat moist for best results; waiting 24-hours after irrigation or significant rain should be sufficient. In contrast, do not aerate immediately after watering, otherwise, you can actually make the compaction worse.
For small areas, inexpensive manual aerators will do. For an entire lawn, consider renting a core aerator from a lawn and garden center or hiring a professional. Make sure to flag sprinkler heads so you don’t damage your irrigation system.
Immediately topdressing with ½” of fine compost and watering it in will allow the compost to filter down into the cores and get to work. The soil cores unearthed in the process can be allowed to disintegrate naturally, or if they are unsightly to you, simply rake them up.
Refer to these links for detailed information:
Excellent, brief publication on good turf management: https://aggieturf.tamu.edu/wp-content
Watch 27:00 to 30:00 in this video presentation given by Texas A&M Agrilife Extension horticulturalist David Rodriguez: https://youtu.be/tp6v5RzyzjM
Question: I’ve had trouble with brown patches in my St. Augustine grass. Is there anything I can do this winter to treat for it?
Answer: Thank you for contacting the Denton County Master Gardener Help Desk with your question about treating your St. Augustine grass for brown patch this winter.
What is brown patch?
Brown patch, also known as Large patch, is a fungal disease (Rhizoctonia solani) that can infect both cool-season and warm-season grasses in North Texas. Symptoms on St. Augustine include circular or irregular brown patches which typically appear in the cooler months when evening temperatures are consistently below 68oF, daytime temperatures are between 75oF and 85oF, and in wet conditions (Jo).
To help you diagnose if your St. Augustine is suffering from Brown patch disease look for yellow leaves at the edges of the patches. The leaf sheath will rot so the leaf blade will separate easily from the runner with a gentle tug (Jo). For a certain diagnosis send a sample to the Texas Plant Disease Diagnostic Lab using the form found at this link: https://plantclinic.tamu.edu/files/2010/10/Plant-Disease-Diagnosis-Form-D-1178.pdf.
Control & Management of brown patch
Your St. Augustine may recover from a light brown patch infection as temperatures rise in the late spring or early summer. Extensively damaged areas may need to be resodded in the spring.
The disease develops more in the following conditions:
- Applying fertilizer in late fall
- Poor drainage
- Watering too frequently
- Mowing lower than 2” to 3” high
- Heavy thatch
Prevention is Key
Brown patch is difficult to get rid of so preventing the disease is critical. The first step to preventing brown patch is to eliminate any of the conditions that promote the development of the disease:
- Improve drainage in areas where the soil stays wet. A thin top dressing of compost applied in early spring will help drainage. If the soil is bare, amend it with 3” of expanded shale and turn it in or till it in 6” to 8”. Apply 3” of compost on top of that (Welsh). Redirect downspouts and check irrigation system zone settings to avoid overwatering poorly drained areas.
- Aerate the soil to decrease thatch.
- Water only in the morning to allow the leaves to dry during the day. And, water only when needed.
- Fertilize with a high nitrogen fertilizer 6 weeks before the first frost which is typically mid-March in North Texas. Reapply fertilizer 3 weeks after the grass greens up in late spring.
- Set the mower blade height to 2” to 3”.
Fungicide effectiveness is limited once symptoms have appeared. It must be applied before or right after the first symptoms appear in October or November. This publication from Texas A&M AgriLife Extension lists fungicides registered for control of brown patch: How to Diagnose and Manage Large Patch Disease in Warm-Season Turfgrass. As always, carefully read and follow the cautions and instructions on the product label.
Sources & Resources
Jo, Ph.D., Young-Ki. “Brown Patch.” plantdiseasehandbook.tamu.edu, Texas AgriLife Extension, Texas Plant Disease Handbook, 31 May 2013, plantdiseasehandbook.tamu.edu/landscaping/lawn-turf/sorted-by-names-of-diseases/brown-patch/.
“D1178 – General Diagnostic Form and Instructions.” plantclinic.tamu.edu, Texas AgriLife Extension, Texas Plant Disease Diagnostic Lab, 1 Jun. 2017, plantclinic.tamu.edu/forms/d1178/.
Jo, Ph.D., Young-Ki. “How to Diagnose and Manage Large Patch Disease in Warm-Season Turfgrass.” https://cdn-ext.agnet.tamu.edu/, Texas A&M AgriLife Extension Service, 1 Feb. 2013, cdn-ext.agnet.tamu.edu/wp-content/uploads/2018/10/E-633-how-to-diagnose-and-manage-large-patch-disease-in-warm-season-turfgrass.pdf.
QUESTION: I am in eastern Wise County near Denton County line. We don’t have a master gardener listed on the website for Wise County, so I was hoping you could help.
I live in my grandparent’s old farmhouse with lawn carved from surrounding pasture. The lawn has never been “lush,” but I would like to improve it to lessen erosion and crowd out sandbur. I’m on well water, so please recommend drought-tolerant turf. Also, can I put ryegrass seed out now, to help with winter erosion, then follow in spring with a warm-season grass?
ANSWER: DCMGA is the correct organization for Wise County residents, so we are happy to help. Although you didn’t mention the type of turf you currently have, the following should be helpful, regardless. First action I recommend is to send a soil sample to Texas A&M to see what your fertilization needs will be come spring. (Link below).
Buffalograss (Bouteloua dactyloides) would be the best warm-season grass for your situation. Buffalograss needs very little water once established. It requires full sun. You will not be able to seed buffalograss until May or June, however.
In the meantime, you can over-seed with ryegrass, if you wish. It will require regular irrigation to establish, then moderate winter irrigation. The best ryegrass variety for your situation is Panterra. In addition to looking pretty, it will help with runoff over winter, but will die out before you want to seed with buffalograss. However, if you prefer not to use well water in winter, simply wait until spring and seed buffalograss.
Before you seed in spring, you will need to prep your planting area. (Links below) You can be as strict about this as you want, but the most important steps would be scalping the existing turf, scarifying the soil so the seeds can land in loosened topsoil and carefully watering during the establishment. Once established, buffalograss is the most drought-tolerant grass for our area.
Question: Are there things I should do now, in August and September, to reduce the number of weeds and improve my lawn next year? I have a combination of St. Augustine in shady areas and Bermuda in sunny areas of my lawn.
Answer: You are a very smart gardener! As Confucius once said, “Success depends upon previous preparation, and without such preparation, there is sure to be failure.” There are several things you can do in August and September to have the lawn that is the envy of your neighbors next year.
- Water in the mornings to allow your lawns’ leaves to dry during the day. Lawns that stay wet over long periods are more susceptible to the development of diseases such as Large Patch Disease.
- Scale back on watering and fertilizing as the temperatures drop consistently below 70o F and as your lawn stops actively growing.
- Mow frequently in August and September and bag/catch your clippings to capture annual weeds’ flowers and seeds. This will reduce their germination next spring.
- Overseed your lawn in the fall when the temperatures are consistently below 72o
- Prepare your lawn to ensure good soil to seed contact by scalping the existing lawn, aerating or vertical mowing (removing thatch). A light top dressing with sand can also help ensure soil to seed contact.
- Follow the seed product labeling for watering to encourage seed germination. Light, frequent watering, often daily, will likely be needed.
- Read the product label carefully if you plan to apply a pre-emergence herbicide to understand which are safe to use for overseeding and the timing before and after overseeding.
- Pre-emergence herbicides are applied before weeds germinate. They inhibit or prevent the weeds from germinating. Post-emergence herbicides are applied after weeds have sprouted and are actively growing.
- Apply the appropriate pre-emergence herbicide for your lawn type and weeds your targeting to significantly reduce the number of annual weeds in your lawn.
- In the fall, apply pre-emergence herbicides in late August/early September. In spring, apply when the soil temperatures are between 50oF and 55oF, typically between mid-February and mid-March.
- Read the product label to understand the pre- and post-overseeding timing. As noted earlier, pre-emergence herbicides can prevent grass seed from germinating.
- Know what weeds you’re targeting and choose the product with the active ingredient(s) that target those weeds. Active ingredients dithiopyr, isoxaben, pendimethalin all target grassy weeds and some broadleaf weeds.
- Always read the entire product label before use and follow the instructions carefully.
Sources and Resources
Texas A&M AgriLife Extension
Question: This heat is frying my zoysia grass, which I put in last year. How many times a week should I water and at what time of day?
Answer: A great choice north Texas, zoysia grass has a superpower that may trick you into thinking the grass is “frying.” When faced with drought conditions, zoysia enters a type of dormancy. This defense mechanism allows it to preserve its precious roots, but in the process, its blades will take on a dry, grayish cast. Turf growth will slow down, as well. With zoysia, this response is normal, and provided you’ve taken reasonable care of your turf, it should perk back up when the heat and drought conditions decrease.
You asked about watering frequency. Deep, infrequent watering promotes healthier turf. The deep moisture coaxes roots into anchoring further into the life-giving soil. In general, your goal should be to dampen the top six inches of soil each time you water, which is about ½” to 1” of irrigation. Many variables affect how long it takes to achieve the goal, such as soil traits, sprinkler head types, humidity, wind, as well as recent temperatures and rainfall. Much of Denton County residents have clay to clay/loam soils. Clay is a sluggish absorber, so using a cycle-and-soak watering method is required to reach the six-inch depth without runoff. (See link, below, for details.)
Regarding what time of day to water, very early morning is optimum. Minimal wind in the early morning allows more of the water to reach its destination. Lower air temperature and higher humidity lessen simple evaporation. Simultaneously, early morning watering protects against fungal infestation, in that the grass blades dry well before nightfall when conditions are greatest for fungal growth.
With early morning watering, you might not notice a broken sprinkler head or split drip line. Each spring, inspect your irrigation system and make repairs accordingly. Some cities offer free irrigation check-ups where a licensed city irrigator will do the inspection for you, noting repairs you’ll be responsible for completing.
Zoysiagrass information: https://aggieturf.tamu.edu
Cycle-and-soak watering method: https://wateruniversity.tamu.edu
Question: We moved to Denton County two years ago and have not been able to keep up with the weeds in our bermudagrass lawn. In all the years of caring for our lawns in other states, we’ve never had this much trouble. Our neighbors said we needed to hire a professional, but we can’t afford it. Can you help us?
Answer: Lawn weeds vex many people new to North Texas, but I assure you, with planning and patience, you can tackle this common problem on your own. No need for a professional! Twice yearly applications of pre-emergent herbicides and timely usage of post-emergent herbicides should remedy your weed problem in time.
In late winter, pre-emergent herbicides should be used 1 to 2 weeks before the average date of our last killing freeze, which is March 18. (You’ll need to move fast to get this round of herbicide down.) Then again in the last week of August or first week of September, a second round of pre-emergent is necessary for treating the cool-season weeds.
Post-emergent herbicides are most effective on young weeds, so they should be applied to warm-season weeds in late May or early June and to cool-season weeds in late October or early November. Aggie Turf provides details on these herbicides, as well as a wealth of science-based information on responsible lawn management, in general.
Question: Is it okay to apply a 3 in 1 fertilizer to my lawn in February?
Answer: We do not recommend weed and feed type products in general because the right time to apply these chemicals is different. A pre-emergent and post-emergent for winter weeds can be applied from mid-February through early March. Be sure to read the package label if you have St. Augustine grass because it is sensitive to some chemicals often found in pre- and post-emergent weed killers. Bermuda is more tolerant. Texas A&M AgriLife recommends having your soil tested before applying fertilizer as healthy, established lawns may not need it. If your lawn does need to be fertilized, it is best to wait until it is actively growing usually after you have mowed two or three times. Here is further guidance from Aggie-Turf for Bermuda and St. Augustine:
Answer: The conditions are perfect for army worms this year, and they are marching across the county. Unfortunately, you may not notice them until they are mature, and by then they can consume an area as big as a football field in two or three days. They feed on the leaves, not the roots, so plants can recover. Bermudagrass is usually okay because it grows so aggressively, but some grasses may die. If there is significant damage, you should treat as soon as possible.
The threshold level for treatment is more than five larvae per square yard. There are many treatment options. If you want an organic option, you can use Bt (Bacillus thuringiensis) or spinosad. This article details each option in order of effectiveness and degree of harm to honeybees and the environment.
Question: I have a very old post oak that is declining. Where can I send a sample to be tested for disease?
Answer: You have some options. First, you can send pictures to the Help Desk at Master.email@example.com. Sometimes we can see signs of fungus or another disease.
Second, you can bring us samples at 400 W. Hickory in Denton. Third, and in this case probably the best option, you can send samples to Texas A&M Plant Disease Diagnostic Lab. Look for forms and instructions at plantclinic.tamu.edu. It will cost a minimum of $35, but they will look at it under a microscope and be able to tell you if there is a disease process at work.
If your tree needs treatment, you can find a certified arborist at isa-arbor.com.
Question: When I drive along the boulevards in my city, I see new trees surrounded by huge mounds of mulch. Should I be using this much?
Answer: Mulch is very important during summer in Texas to reduce water loss from the soil and to moderate soil temperature. In addition, if you use an organic source (e.g., leaves, grass clippings, wood chips) for your mulch, it will slowly break down and enrich your soil.
You can, however, use too much of a good thing. The thick piles you see are called volcano mounds and are not good practice. Tree roots need oxygen, and piling mulch a foot deep is similar to covering your nose and mouth. You wouldn’t last long, and neither will the tree! Spread mulch no more than 3-4” deep, and rake it a few inches away from the trunk. The same goes for all plants; keep the mulch away from the stems.
For more information and discussion of different types of mulch
Question. Moles are tearing up my yard! What can I do?
Answer: They are eating grubs and aerating your soil, but most people do not find that sufficient reason to keep them around. The first thing to know is that most repellents do not work. You need a mole trap.
You also need your wits, however, because you need to think like a mole to trap one. They use some tunnels more frequently than others. Think of it as the difference between a highway and a side road. Finding an active runway is key. How do you know which tunnel is active? Step on it at night. If it is active, the mole will dig through it that night, and it will be raised up in the morning. That’s where the trap goes, and your chances of catching the critter go up. Details and a discussion of various types of traps
Question: The guy who cuts my grass told me to run each irrigation station 10 minutes three times a week, but my grass looks pitiful.
Answer: There are many variables, such as the type of grass, type of soil, amount of rainfall, the flow rate of your sprinklers, etc. The goal is to dampen the soil about 6” deep. This means you need to apply about 1/2-1” each time you water. The easiest way to find out how long it takes your system (manual or automatic) to water one inch is to place flat bottom cans in different locations around the yard. Run your system 30 minutes and measure how much water is in the can. Let’s say it’s 1/2”. Allow the water to soak in for about an hour and then take a long screwdriver and push it into the soil until it stops. If the soil is damp up to 3” deep, then you need to run your system another 30 minutes. If it goes easily into the soil the entire 6”, then you have watered enough. On heavy clay, watering once a week is probably enough. On sandy soils, you may have to water every 5-6 days. Watering more frequently and shallowly will cause the grass to have shallow roots, which is not what you want for healthy grass.
Question: My lawn guy says he thinks my grass has TARR (take-all-root-rot). Can you tell me about it and tell me how to cure it?
Answer: Moist spots in stressed grass are more likely to see this fungus in late spring or early summer. Before treatment, be sure you have TARR (take all root rot) rather than two look-alikes: brown patch (a different fungus) or chinch bugs, which are also active in the summer. Each one is treated differently. This article details diagnosis as well as treatment options for each condition.
TARR treatment includes lowering the pH, which can be accomplished with applications of peat moss a couple of times a year, and fungicides in the spring and fall. Preventive measures include improving drainage and aeration, reducing thatch, and watering infrequently but deeply.
Irrigation mistakes are extremely common and account for many instances of fungus and other diseases. Next week we will address how to irrigate your lawn properly.
Question: How can I get grass to grow under my trees?
Answer: The short answer is that you can’t. Grass needs at least six hours of sunlight a day, and your thinning bare patches, particularly near the trunk, prove it. Our most shade tolerant grass is St. Augustine, but even it will not grow in dense shade. Some fescues are shade tolerant and cold hardy. However, they require a lot of water during the summer, and even they will not tolerate heavy shade.
You could cut down your trees and grow grass, but your property would suffer a loss of value, and your electric bill would probably go up. Your choices are to (a) prune your tree to allow more sunlight (remembering that leaves provide nutrition for the tree, so leave some!) or (b) use a shade-tolerant groundcover.
Question: When should I apply pre-emergent herbicides to my lawn?
Answer: Apply in early spring (late February-mid March) for summer weeds. Apply in early-mid September for winter weeds. Pre-emergents work by preventing seeds from germinating, so the weeds you see now have already germinated, and a pre-emergent will not work. You can apply a post-emergent weed killer for weeds that have already appeared. But be careful. There are different types of herbicides. Some are targeted to a particular plant (selective herbicide), whereas others kill every plant contacted (nonselective herbicide). For instance, if you apply a grassy weed killer in dormant grass, it might affect the grass you wanted to keep. St. Augustine grass is particularly sensitive to herbicides. Read the label, and never apply more than the recommended rate.
Question: I just moved to a new house. I have no idea how to take care of the lawn.
Answer: The Aggie Turf website has more information that you probably want about lawn care, including selection, establishment, fertilization, watering, etc. Since you are not familiar with the soil, first get the soil tested. For information about how and where to send a soil sample, see the Texas A&M AgriLife Soil, Water and Forage Testing Laboratory page.
Question: My St. Augustine grass is looking really bad.
Answer: St. Augustine has been beset by problems this year. Last year’s extreme cold was very stressful, and the extreme heat of summer combined with high humidity added more stress. The cold followed by heat and humidity is the perfect environment for fungi. Watch for gray leaf spot which shows up as brown lesions on the leaf. To reduce the severity of gray leaf spot, avoid applications of soluble nitrogen fertilizers on moderately shaded lawns during summer months. Herbicide applications which may weaken St. Augustinegrass should also be avoided on shaded lawns. Apply water to the lawn in early morning only when water is needed. Avoid late afternoon and evening watering which keeps the leaf surface moist for long periods. Also, catch grass clippings in lawns where gray leaf spot is a problem.
Also watch for brown patch, which forms circular brown patches. If you want a definite diagnosis, you can send a sample to the Texas Plant Disease Diagnostic Lab. For a fee, they will diagnose your ailing plants.
Question: Feral hogs rooted up my lawn and left a huge muddy mess. Can I overseed now with rye (November)?
Answer: You can, although overseeding is not usually recommended due to its competition with the warm season grass the following spring/summer. In your case, it might be best to control erosion during the winter. The option, although expensive, would be to sod with the grass of your choice.
Answer: Thank you for contacting the Denton County Master Gardener Association with your question about your nectarine tree. We have received several inquiries lately about this issue in nectarine and peach trees. It appears your tree is suffering from the fungal pathogen Botryosphaeria dothidea, commonly known as Fungal Gummosis.
Fungal Gummosis is a vascular disease that limits the growth and production of stone fruit trees such as peaches and nectarines. Large amounts of resinous compounds exude from fungal infections at lenticels (essentially pores in the bark) or from other entry wounds on branches or tree trunks. These symptoms are brought on by physical injuries such as damage by insects or string trimmers or chemical injuries. Secondary pathogens infect the wounds leading to fungal gummosis.
Early symptoms are raised blisters near wounds or on young shoots. These lesions continue to expand under the bark clogging the tree’s vascular system resulting in limb dieback and cankers on the bark. In severe infections, the outer corky protective layer of woody stems will be very coarse with a blackish color. Severe infections ultimately result in the death of the tree.
According to the University of Florida Horticultural Sciences, disease management of fungal gummosis is very difficult. The infection can occur almost any time of the year, and, once the tree is infected it is difficult to control the infection in the inner tissues of the tree. There are no approved fungicides to treat fungal gummosis specifically. However, fungicides for treating fungal diseases in the fruit and leaves of fruit trees may help in suppressing fungal gummosis.
There are several horticultural practices for managing a fungal gummosis outbreak.
- Pruning practices:
- Avoid pruning when the tree is wet following rain or irrigation
- If the tree is stressed from lack of water or nutrition, do not prune
- Prune healthy trees first and, infected trees last
- Disinfect the pruning equipment each time after pruning infected trees with rubbing alcohol or a weak bleach solution (10% bleach, 90% water)
- Spray pruned branches and twigs with a fungicide afterward to protect the fresh wounds
- Discard pruned or downed limbs and fruit in the trash, do not compost them
- Promote air circulation:
- Properly prune the tree’s branches to open up the canopy for air circulation. This link from Oregon State University Extension shows how to properly prune fruit trees: https://catalog.extension.oregonstate.edu/pnw400/html
- Remove suckers from the base of the tree
- Keep weeds and grass from growing up around the base of the tree; they reduce air circulation around the trunk
- Other practices:
- Water the root zone only using drip irrigation or a soaker hose; avoid wetting the bark, leaves or twigs of the tree especially after pruning or harvesting
- Proper fertilization will avoid excessive growth of young shoots that are particularly susceptible to fungal gummosis
- Monitor the tree daily for signs of wounds from insects, rabbits, or deer and mechanical damage from string trimmers or mowers
- Look for lesions on the bark to detect fungal gummosis to help you understand the disease severity and possible spread to other fruit trees
- Plant fruit trees in well-draining soil; correct any drainage issues if the tree is periodically in standing water
Sources and Resources
Texas A&M AgriLife Extension Plant Disease Handbook, description and photos of the diseases that can affect peach, apricot and nectarine fruit trees: https://plantdiseasehandbook.tamu.edu/food-crops/fruit-crops/peach-apricot-and-nectarine/
“Home Fruit Production – Stone Fruit” from Texas A&M AgriLife Extension, information about growing fruit trees in Texas: https://aggie-horticulture.tamu.edu/extension/homefruit/stone/stone.html
“Homeowner’s Guide to Pests of Peaches, Plums, and Pecans” from Texas A&M AgriLife Extension, information about the common insects and pests of peaches, plums, nectarines, and pecans: https://agrilifeextension.tamu.edu/library/gardening/homeowners-guide-to-pests-of-peaches-plums-and-pecans/
“Fungal Gummosis in Peach” from University of Florida IFAS Extension, information about fungal gummosis disease and management: https://edis.ifas.ufl.edu/hs1265
Question: Every year my vegetable garden gets overrun with aphids. I have tilled my soil, planted naturally repelling plants, I use a neem and soap combination spray, and I spray aphids off the plants with water, yet they always get the upper hand. This year I was considering tenting my plants with netting and releasing beneficial insects like ladybugs or katydids to help. Do you have any recommendations on places to purchase non-invasive insect species (I don’t want to release more Asian Lady Beetles!) or any other recommendations to fight off these nasty buggers?
Answer: It sure sounds like you’re doing all the right things to try to control aphid infestation in your vegetable garden. There are few additional tips from John A. Jackman of Texas A&M AgriLife Extension that you might consider this year.
- Putting a reflective mulch such as foil paper on top of the soil below your plants can slow aphid infestation
- In early spring or early fall, when it is not blistering hot, put a fine mesh screen or fabric over your garden. Your plants will still need to be monitored regularly, preferably daily, so you will need to remove the barrier. It’s not recommended to leave barriers in place during the hot summer months because the temperature inside the barrier is warmer than outside of it so it can cause your plants to suffer from heat stress.
- High-pressure water sprays can dislodge aphids. You will need to repeat this treatment frequently.
- Use pesticides, Neem oil, and insecticidal soaps only as a last resort because these products will also kill the beneficial insects that naturally control aphids.
These tips, as well as a list of registered pesticides for use on home garden vegetables and common insect pests, can be found at this link: https://agrilifeextension.tamu.edu/library/gardening/managing-insect-and-mite-pests-in-vegetable-gardens/
Other cultural practices you may want to consider include:
- Remove any plant debris, soil residue and dispose of weeds or other unwanted plants that pop-up to get rid of the food and shelter before planting and throughout the growing season. When the growing season ends, remove these things as well so aphids will not overwinter there. Also, control of aphids is easiest after soon after they hatch from the eggs. Look for egg clusters or tight groups of eggs on the undersides of the leaves. You can gently scrape away the eggs or remove them with a blast of water. Website link: Chapter VI: Insect Management James Robinson
- Although there’s no scientific data to support this practice, some gardeners claim it is helpful to use trap plants or sacrificial plants that attract aphids to draw them away from your vegetable plants. Examples include nasturtiums and sunflowers. Be careful not to plant these too close to your vegetable plants to avoid the aphids traveling to them. In addition, consider planting plants that repel aphids amongst your vegetable plants. Plants that repel aphids include those of the allium family (garlic, chives, leeks), marigolds, or catnip, fennel, dill, and cilantro. Website link: Trap Plants For Aphids: Plants That Repel Aphids In The Garden
In discussing your issue with other Denton County Master Gardeners, we had a few questions and ideas you may want to think about that may be contributing to your aphid issue:
- Are there other plants nearby in your yard or your neighbor’s that may be attracting aphids to your vegetable garden? For example, the Cotton or Melon Aphid (Aphis gossypii Glover) food sources include begonia, catalpa, citrus, ground ivy, hydrangea, violets, and weeds as well as vegetables. Green Peach Aphid (Myzus persicae (Sulzer)) has a wide range of food sources including peaches, some flowering ornamental plants and, vegetables. Website link: Aphids in Texas Landscapes
- Are you practicing crop rotation each year? For example, not planting tomatoes or peppers which are both members of the nightshade family in the same place each season.
- Healthy vegetables can withstand some aphid damage but stressed plants are much more susceptible to insect damage. Practicing good irrigation, mulch, and fertilization habits go a long way toward growing healthy vegetables that can tolerate some insect damage and still produce for you.
- The beneficial insects you introduce will stick around only as long as there’s a food source. Once there’s no food source, they’ll move on. We think it may be better to use the row covers as you described, limit your use of pesticides including insecticidal soap to avoid killing the beneficial insects that occur naturally and practice the other cultural control methods mentioned above.
Sources and Resources
Jackman, John A. “Managing Insect and Mite Pests in Vegetable Gardens.” agrilifeextension.tamu.edu, Texas A&M AgriLife Extension, 1 Feb. 2008, agrilifeextension.tamu.edu/library/gardening/managing-insect-and-mite-pests-in-vegetable-gardens/.
Robinson, James. “Managing Insect and Mite Pests in Vegetable Gardens.” aggie-horticulture.tamu.edu, Texas A&M AgriLife Extension, 1 Jan. 2009, aggie-horticulture.tamu.edu/vegetable/guides/texas-vegetable-growers-handbook/chapter-vi-insect-management/.
Baessler, Liz. “Trap Plants For Aphids: Plants That Repel Aphids In The Garden.” gardeningknowhow.com, Gardening Know How, 4 Apr. 2018, www.gardeningknowhow.com/plant-problems/pests/insects/plants-that-repel-aphids.htm.
Jackman, John A., and Robinson, James. “Aphids in Texas Landscapes.” agrilifeextension.tamu.edu/, Texas A&M AgriLife Extension, 1 Mar. 2011, agrilifeextension.tamu.edu/library/landscaping/aphids-in-texas-landscapes/.
Question: I would like to propagate blueberries using hardwood cuttings, but I’m having trouble finding information about it. Could you help me?
Answer: This one really took some digging (no pun intended)! Information on blueberry propagation, especially from hardwood, is not always easy to find.
Blueberries are propagated using shoots (“whips”). Whips are usually obtained from the previous season’s growth and are about 12-36 inches long. As with any propagating, make sure you select cuttings from a healthy plant. Whips are best obtained in late winter or very early spring, just before bud growth begins. Do not use shoots formed in late season. Cuttings should be from past season’s growth, mature and firm. The optimum diameter is one-quarter inch.
Cuttings are generally four inches long with four buds. The length of the cutting can be shorter if necessary. When making the cutting, avoid bruising or crushing the tissue. The best tools are sharp, clean and properly adjusted pruning shears, or a sharp, clean, knife.
Percent rooting tends to decrease progressively as cuttings get closer to flower buds. The best rooting response is seen when the distal (top) cut is made directly above the highest bud, and a slant cut is made just below the lowest bud.
As a rooting medium, a mixture of peat, perlite, and potting soil is good. Some prefer to use pure peat. It should be at least four inches deep. The medium should be soaked for three to four hours prior to planting. Cuttings are pushed vertically into the medium until only the top bud is exposed and should be about two inches apart.
Examine the soil each day for moisture level. Keep the propagation beds moist, but not soaked. Misting is also helpful. You may choose to apply a liquid fertilizer weekly. If you do that, make sure it is diluted. The cuttings may take three to four months to root and can typically stay in the propagation bed until winter. After that, they may be planted into pots or nursery beds for one year, until the next winter. Thereafter, the plants should be of sufficient size and vigor to be planted in the garden or landscape.
Refer to the following document for detailed information: https://blueberries.extension.org/blueberry-propagation/
QUESTION: I want to plant thornless blackberry bushes this fall. My husband grew up in Washington state near a berry farm and said that blackberries grow aggressively. Are less-aggressive varieties available that will grow well in north Texas?
ANSWER: As a child, I relished picking fresh, wild blackberries, warm from the sun! A wonderful option in North Texas, cultivated blackberries delight the senses just as well as the wild ones, with less aggressive growth. The thornless variety recommended for our area is Natchez, a semi-erect plant that requires some simple trellising in the second year. Late winter is the right time to put in root cuttings, but dormant plants can be planted anytime, although early spring is optimal. Blackberries need excellent drainage, so you may need to plant in berms of compost-amended soil.
With regard to aggressive growth, it would be best to corral these vigorous plants behind in-ground metal edging or another barrier and to pull any young shoots from undesirable locations. Make sure to keep branch tips away from the soil, as they will propagate themselves via this “layering,” as well. The cultivated varieties are not as aggressive as the wild, thankfully, but as with any hardy plant, you’ll want to keep a watch on its growth.
The articles below offer excellent recommendations.
Question: I would like to grow vegetables this fall but I don’t know where to start! What should I do with my spring vegetable garden plants? Do I need to do something to the soil to get it ready? What vegetables can I grow and when should I plant?
Answer: Fall is a wonderful time to grow vegetables here in North Central Texas. The fall climate is much more conducive to both plants and humans! There are fewer issues with insects and damage from the hail storms we sometimes have in the spring. That being said, the steps to take to be successful with a fall vegetable garden are somewhat different than spring or summer.
Choose and prepare the garden site: You can use the same site as your spring/summer vegetable garden as long as it receives the requisite 6 – 8 hours of sun daily in the fall. If you’re planning to use a new location for your fall garden, it should be 6 feet (minimum) away from shrubs or trees to ensure full sun exposure, have good drainage and access to irrigation. There are some things you need to do to prepare the soil for the fall growing season:
- Remove all spring/summer vegetable plants that have run their course. The plant material should not be composted if it has or had any fungal or bacterial pathogens.
- Dig out, do not till under, any weeds or grass that may have grown in the garden.
- If it’s a new garden bed, shovel or turn under the soil 10” to 12”.
- Replenish the soil with 2” to 3” of organic material such as fully composted manure. If it’s a new garden bed, also add 1” to 2” coarse sand.
- Add slow-release fertilizer at the rate of 2 to 3 pounds per 100 square feet.
- Work all of these into the soil 4” to 6” with a garden fork. Tilling the soil is not recommended as it breaks down the soil structure.
- Deeply water the area for about 2 hours, then allow to dry for 2 days. Now your garden is ready to plant!
Choose your plants: As with the spring vegetable garden, grow the vegetables you and your family like to eat.
- Due to the short growing season, planting transplants rather than direct seeding is recommended except for beans, peas, beets and carrots, which do not transplant well.
- Timely planting is critical to a successful harvest. In North Central Texas, November 15 is the average first frost date. There are two ways to determine when to plant each variety:
- Calculate it: # of days to maturity + 14 days = the number of days to count backward from November 15 for your planting date
- Look it up: Use the Texas A&M AgriLife Extension Vegetable Planting Guide for North Central Texas, found at this link: https://dallas-tx.tamu.edu/files/2010/06/Vegetable-Planting-Guide.pdf
- Group your plantings by tolerance to frost. In other words, plant frost susceptible vegetables together and frost tolerant vegetables together.
- Frost susceptible vegetables: Bean, corn cucumber, eggplant, okra, pea, pepper, squash, tomato, watermelon
- Frost tolerant vegetables: Beet, broccoli, Brussel sprout, cabbage, carrot, cauliflower, chard, collard, garlic, kale, lettuce, mustard, onion, parsley, spinach, turnip
Care for your garden: Water
- Your new transplants may need to be watered daily during September which can be just as hot as late summer. A general rule of thumb is to water new plants daily for the first 14 days after transplanting in the garden to give their root system time to establish.
- Otherwise, your garden should receive 1” to 2” of water once weekly including any rainfall.
- If the soil is dry 1” down, it’s time to water. Or, take the guesswork out altogether and purchase an inexpensive soil moisture meter.
- Protect from insects, late summer sun, and cold
- Although the insect pressure is lower in the fall, you’ll still need to monitor your plants daily for pests.
- If you choose to use chemical controls, choose the insecticide that is appropriate for the target insects and plants. Read and follow the label instructions carefully.
- Consider covering your plants with transparent plastic, vented during the day, or .5-ounce spunweb which doesn’t need to be vented. Spunweb covering not only will help protect against insects, it can also help filter the sun and temper the heat during September.
- Extend the growing season and protect against frost by covering with 1.5-ounce spunweb material, often referred to as “frost cloth”. Avoid letting plant covers touch the leaves by using hoops, frames or cages around your plants under the cover.
Harvest your produce: Harvesting the efforts of your hard work is also a matter of the right timing and method. This guide from Texas A&M AgriLife Extension provides a wealth of information about how and when to pick and store your vegetables: Easy Gardening, Harvesting, Handling, and Storing Vegetables, https://aggie-horticulture.tamu.edu/vegetable/files/2010/10/E-510_harvesting.pdf. A few special call-outs:
- Spinach and many greens leaves can be cut throughout the growing season to encourage resprouting, often referred to as “cut and come again”.
- To “blanch” your cauliflower heads, wrap the leaves over the head and pinch together with a clothespin or clip.
- Carrots can be stored in the soil for several weeks after they mature.
- Harvest tomatoes when they’re pink if they’re in danger of frost. They can be ripened indoors in a warm area.
Sources and Resources
Texas A&M AgriLife Extension, Denton County Master Gardener Association, Vegetable Gardening in North Texas
Texas A&M AgriLife Extension, Fall Vegetable Gardening Guide for Texas
Question: When should I plant broccoli, cabbage, and other winter vegetables?
Answer: A big advantage of winter gardening is that there are far fewer insects. Broccoli, cabbage, lettuce, carrots, and cauliflower can be planted any time until late September. It’s a little late for potatoes and right on the cusp for squash. List of North Texas vegetable spring and fall planting dates.
Question: My tomato plant has spots on the leaves. What is wrong with it? Do I need to spray it?
Answer: There are so many tomato conditions and diseases that A&M wrote a whole section of their horticulture website to help you solve it. It is divided into problems with fruit, leaf, stem, root, and insects. Cleverly enough, they called it “Tomato Problem Solver.” It has great pictures so that you can identify your problem, and it will also tell you what to do about it.
Question. Why are tomatoes so fussy in our area? What varieties will do well here?
Answer: That is one big question, and we should have a tomato class to explain it all! But we will try to break it down. First, tomatoes cannot pollinate well when daytime temperatures are above 90 or nighttime below 70. Now think about when our temperatures start doing that. Early, right? So, you must plant them very early to get the best harvest, and then prepare to cover them if we have a late frost. Because many older standby varieties are no longer available.
Be aware that some stores selling tomato plants may have varieties that are challenging to grow here in North Texas. A general guideline is to select small to medium-sized types rather than the very large ones that do better further north. Neil Sperry, in a recent Facebook post, suggested trying Celebrity, Porter, Roma, Cherry, Sweet 100 or Yellow Pear.
Secondly, some tomato varieties produce again in the fall and some do not. When you buy a transplant, the label should indicate whether it is “determinate” or “indeterminate”. Determinate plants have a big, showy production for a couple of weeks, and then they are done. These plants are bushier and don’t get as tall, and if you want to make tomato sauce, you would look for a determinate plant. But indeterminate plants continue to grow taller and taller. They will stop producing when it gets hot but will resume production when temperatures moderate in the fall.
Thirdly, the variety you plant may or may not be adapted to our extreme heat. Unfortunately, there are not many seed companies left, and they cater to the big tomato producing areas on the East and West coasts. So many of the heat tolerant varieties you relied on in the past are simply not available anymore. Dr. Jerry Parsons discussed this in the following article.
How about heirlooms, you ask. Sure, go for it if you want. Just know in advance that their production is light, and you will most likely fight insects and diseases. There is an old saying here that heirlooms are the best way to get a $2.99 tomato for a few hundred dollars. But they do taste wonderful, and it might be worth it to you.
Question: I’m bewildered by the huge number of vegetables available in stores and online. Is there a list of what does well here? And how do I know when to plant what?
Answer: Here’s a great resource for when to plant, how deep, and how far apart. Vegetable Planting Guide. And here are two resources for recommended cultivars for North Texas: Recommended Vegetable Varieties and Vegetable Variety Selector (enter your county and recommended cultivars appear as a list).
Question: I’m a new gardener and would like to start a vegetable garden this year. Where do I start?
Answer: Start with the one page “Beginner’s Guide to Vegetable Gardening” on the vegetable page of our website. In five easy steps, you will find soil, sun and water requirements as well as links to specific varieties that work well in Denton County. If you are working with existing soil in a row or raised bed, getting a soil test to see what minerals and nutrients are needed is a good way to start your preparation for planting. You can get your soil tested through http://soiltesting.tamu.edu/. Their website explains how to collect a soil sample and complete the submission forms. Additional information is available from Introduction to Vegetable Gardening presentation and once you get started, there is extensive information here: https://dcmga.com/north-texas-gardening/vegetable-gardening/
Question: Can I save vegetable seeds for next year?
Answer: This is a fairly complicated question. Hybrid vegetable seeds will not reproduce as you might expect. If you are determined to save seeds, designate a few plants to allow to seed and take precautions to be certain they are not cross-pollinated. See this article about hybrid varieties and saving seed for a full discussion of hybrid seeds, which seeds you can save, and how to prepare them.
Question: Will my spring tomatoes produce more fruit in the fall?
Answer: It is possible if you have indeterminate tomatoes (they continue to grow taller throughout the season) that are still healthy. Most of the determinates will shrivel and die during the summer.
Question: Can I locate my vegetable garden over the septic leach field?
Answer: It is possible but probably not advisable. This is a quote from the Virginia Cooperative Extension Service: “Sometimes the ideal place to put a vegetable garden seems to be over the leach field, raising the question of bacterial and viral contamination from the effluent. Soils vary a great deal in their ability to filter viruses and bacteria. Clay soils work best, eliminating bacteria within a few inches of the drain trenches, but sandy soils may allow bacterial movement for several feet. A properly operating system will not contaminate the soil with disease-causing organisms, but it is very difficult to determine if a field is operating just as it should. If at all possible, use your septic drain field for ornamentals and plant your vegetables elsewhere. If you must plant vegetables, take the following precautions. Do not plant root crops over drain lines. Leafy vegetables could be contaminated by rain splashing soil onto the plant, so either mulch them to eliminate splashing or don’t grow them. Fruiting crops are probably safe; train any vining ones such as cucumbers or tomatoes onto a support so that the fruit is off the ground. Thoroughly wash any produce from the garden before eating it. Do not construct raised beds over the field; they might inhibit evaporation of moisture.”
Question: What is wrong with my grapes?
Answer: Under the microscope, we found larva that looked like this picture. Your grapes have grape berry moth. For control, see this berry moths information article.
Question: What kind of black-eyed peas do well in Denton County?
Answer: Blackeye #5, Colossus, Mississippi Silver, Pink Eye purple hull, Texas Pinkeye, or Zipper Cream. For other vegetable and fruit recommendations, see the Vegetable Variety Selector.
Question: What variety of peach and pecan trees do well here?
Answer: PEACHES are not the easiest fruit to grow in Denton County, but these are the recommended varieties: Springgold, Bicentennial, Sentinel, Harvester, Ranger, Redglobe, Fire Prince, and many others. For more information, see the Home Fruit Production — Peaches page.
It is very difficult to grow peaches organically. A well-timed spray schedule will increase your chances of getting good fruit. This article will give instructions and timing.
PECANS: Sioux, Choctaw, Wichita, Cheyenne, Pawnee, Forkert, Cape Fear, Kiowa, Caddo. For more information regarding growing pecan trees, including pruning, fertilizing, pests and diseases, go to the Aggie Horticulture Home Fruits – Pecans page.
Question: The leaves on my favorite rose of sharon started browning last week, and now, the plant looks nearly dead. I’ve included a photo. What could have happened? If I can’t save it, can I re-plant a new rose of sharon in its place?
Answer: What a heartbreak to see such a beauty fail so rapidly. Diagnosing disease from photos alone is a challenge; however, the most likely culprit is cotton root rot (Phymatortrichum omnivorum). Rose of sharon is highly susceptible the fungus, which is active during this time of year and advanced by overwatering. Is it possible that you could be overwatering in an attempt to save the shrub? Or could there be an irrigation/pool leak in the area?
Before giving up on your plant, first correct any water or drainage issues you may have. Run each zone of your irrigation system for a minute or two. Put on your raincoat and wellies and look closely at each sprinkler head and your entire drip line. Sometimes water will spew like a geyser; other times, you’ll see bubbling water at the base of sprinkler heads or a flowing stream from your drip lines. If you see leaks or misdirected sprays, correct them. Do this check every month you use irrigation. This link gives easy guidance: https://wateruniversity.tamu.edu
Next, get into the habit of checking soil moisture before running irrigation. Use a screwdriver to probe the soil to a depth of 6-8 inches. If you’re able to probe to that depth, moisture is sufficient and no watering is necessary. Alternatively, invest in an inexpensive (<$5) soil moisture meter, and spot-check your landscape before watering (to the same 6-inch depth).
If you’re not able or inclined to manually check the soil, or if you travel, then consider upgrading to a smart controller. It uses your local weather station’s current evapotranspiration (ET) readings to calculate irrigation. (ET refers to evaporation that comes from the soil itself as well as from the plants’ leaves.) The controller doubles as a rain/freeze sensor, shutting off when temperatures drop below freezing or when local rain exceeds a set threshold. Once installed and linked to your WiFi, these smart controllers can be programmed and adjusted from the controller itself, or from your smartphone, tablet or computer.
This webpage explains how to use a probe or screwdriver to gauge moisture, as well as gives details on rain-freeze sensors and advanced controllers: https://wateruniversity.tamu.edu/irrigation
The following document describes how to possibly save ornamental plants suffering from cotton root rot by using ammonium sulphate to acidify the soil, creating an unfavorable growing condition for the fungus. This option is a last resort, but it is inexpensive and fairly easy, so it might be worth a try. The downside is that you’ll have to continue acidifying the soil every year, which may become tiresome. In short, prune the shrub back. Build a ridge of soil about four-inches high around the tree’s drip line. The circumference of the ridge-line should be equal to the diameter of the crown/top of the tree. Work into this soil one pound of ammonium sulphate for every 100 square feet of area within the ridge. Fill the ridge with water to a depth of four inches. Repeat this treatment five to ten days later. Limit treatment to twice per season. Refer to the section at the end of the article entitled “Fertilizer Applications.”
If your shrub dies completely, and you wish to replant another rose of sharon, do not replant it in the same location, since the fungus remains active in the soil for years. Instead, plant it in a sun/part-sun location where drainage is excellent. These beauties like moist soil, but not standing water. In its place, plant a flowering shrub resistant to cotton root rot (see link below).
Cotton root rot: https://bexar-tx.tamu.edu/homehort
New rose of sharon varieties: https://agrilifetoday.tamu.edu
Trees, shrubs and flowering plants with resistance to cotton root rot:
Question: I have over 60 daylilies that have been in their current location five years, and until this year, they have had tall scapes and lush foliage. This year, the leaves are turning yellow and the scapes are very short. What is happening?
Answer: Daylilies often seem so carefree and hardy that their health is easy to take for granted. In trying to find clues to your daylilies’ stress, you will want to check for insects and pests as detailed below, but first let’s consider their overall environment and next their specific physical condition.
It seems that your daylilies have been performing satisfactorily for five years where they are planted now, but that their decline has been sudden this year. Here are a few questions about possible changes in their general environment:
- Could your daylilies have been exposed to herbicide applications like “Weed and Feed” or any other herbicide through spray, run-off or drift?
- Has shade been encroaching on their beds over the years? Daylilies need at least 6 hours of sun daily for best blooming, though they will tolerate filtered light. This is probably not responsible for a sudden decline but can cause spindly growth and lack of blooms.
- Have there been any interruptions in the bed’s drainage (construction or something else)? The beds should be able to hold moisture but also be well-drained.
- Overwatering, overhead watering, and poor drainage can be the source of bacterial root rot and fungal disease. Overcrowding and poor air circulation may be a cause of disease and insect infestation. For this reason, daylilies should be divided every three to five years, preferably in the early fall.
Daylilies can do well over a relatively wide soil pH range and adjustment of pH need only be considered if the plants appear to be doing poorly, which yours are. I advise that you submit a soil sample for testing to Texas A&M soil lab. This will give you information for the pH and nutrient characteristics of your soil, as well as recommendation for adjustment, if it is necessary. The link to the Texas A&M University Soil Testing Lab is below.
As soon as possible, you can check drainage and possible overcrowding. You need to inspect the daylilies for signs of disease and pests, using the Clemson Cooperative Extension article linked below as your guide. It gives descriptions of common diseases (daylily rust, leaf streak, root rot, etc.) and pests that afflict daylilies and how to control them. We have had a very warm winter, so the surviving spider mite population, for instance, will be large and hungry. A serious case of rust or infestation of spider mites could be the immediate cause of your problems, but some environmental or cultural adjustments may also be in order to correct underlying conditions.
However, for a definite diagnosis, you may also submit a sample to the Texas A&M Plant Disease Diagnostic Lab (about $35).
TAMU Plant Disease Diagnostic Lab: https://plantclinic.tamu.edu/
Texas A&M soil testing lab (A basic soil test is $12; use the Urban/Homeowner submittal form.): http://soiltesting.tamu.edu/
Question: I live in Oak Point and was wondering if I can use a pre-emergence product on a rose bed where mature roses have been growing for several years. I wondered if a pre-emergence would help control weeds or would damage the roses.
Answer: Weed control in ornamental beds is a constant chore. There are several methods for weed management including mechanical removal, mulching or sheet mulching and, chemical control. Let’s walk through the pros and cons of each in managing the weeds in your mature rose bed. According to John F. Karlik of the University of California Agriculture & Natural Resources, in most home rose garden beds, mulches supplemented with regular hand weeding should provide enough weed control.
Mechanical Weed Removal
Roses are shallow-rooted plants so care needs to be taken when mechanically removing weeds. Using hand tools is best rather than hoes to avoid damaging the roses’ roots. My favorite is a Hori-Hori garden knife. Remove the weeds when they are young before they go to seed. Attempt to remove the entire weed plant including the roots.
Mulching or Sheet Mulching
John Karlik recommends mulching with 2 to 4 inches of organic material such as wood chips to reduce annual weeds and make hand-weeding easier in the rose bed. I have personally found sheet mulching to be the most effective method for reducing weeds in my ornamental beds.
Sheet mulching also referred to as sheet composting or lasagna composting is an excellent way to control broadleaf and grassy weeds in your ornamental beds while improving the soil at the same time! Here are the steps I take every spring, usually after the last frost, to prepare my ornamental beds for the growing season:
- Start by mechanically removing any weeds or grass in the beds.
- Pull back any existing mulch and cover the soil with overlapping layers of cardboard or several layers of newspaper. The carbon in these materials smothers the broadleaf and grassy weeds.
- Thoroughly wet the cardboard or newspaper covering and add a layer of fully composted material to add nitrogen. Composted manure is a good choice.
- Top that layer with 2” to 4” of mulch such as wood chips.
- These layers will decompose over time improving the condition of your soil by adding microbes and nutrients to the soil that your plants need to be healthy.
Woven landscape fabric can also be placed over the soil and then covered with mulch to provide weed control. This material, of course, does not improve the soil as sheet mulching does.
There are preemergence herbicides that can be used around roses before weeds emerge. John Karlik recommends preemergence herbicides with the active ingredient oryzalin or pendimethalin which have been effective in field trials and did not injure the rose plants. Preemergence must be applied when the soil temperatures are below 55 degrees and air temperature is consistently below 70 degrees. In North Texas, this is typically mid-to-late March.
To control grassy weeds that have already emerged, John Karlik recommends
postemergence herbicides with the active ingredients fluazifop-p-butyl or clethodim which were also effective in field trials and did not injure the rose plants.
Mr. Karlik also warns against using any broadleaf postemergence herbicides around roses such as 2,4-D, triclopyr, and dicamba as roses are sensitive to those chemicals. In addition, non-selective herbicides such as glyphosate should not be used near roses.
Always check the labels of each herbicide before using for labeled bedding plants, susceptible weeds and any precautions that should be observed.
Combine All 3 Methods for Success
You will likely need to combine all three methods – mechanical removal, mulching, and chemical control – to completely control the weeds in your rose beds. The combination of mulching/sheet mulching and using preemergence herbicides can make a real reduction in the amount of hand weeding needed during the growing season.
Sources and Resources
Karlik, John F. “Roses: Cultural Practices and Weed Control.” ipm.ucanr.edu, University of California Agriculture & Natural Resources, 1 Jul. 2019, ipm.ucanr.edu/PMG/PESTNOTES/pn7465.html.
Trinklein, David. “Weed Control in Ornamental Beds.”ipm.missouri.edu, University of Missouri, 9 Jun. 2016, ipm.missouri.edu/MEG/2016/6/weed_control/.
“Sheet mulching — aka lasagna composting — builds soil, saves time.” oregonstate.edu, Oregon State University Extension Service, 1 Feb. 2004, extension.oregonstate.edu/gardening/techniques/sheet-mulching-aka-lasagna-composting-builds-soil-saves-time.
Question: I have noticed scale on my Crape Myrtles. How do I treat this?
Answer: Thank you for contacting the Denton County Master Gardener Help Desk with your question about how to treat scale on your crape myrtle trees. Your trees are likely infected with a crape myrtle bark scale (CBMS, Acanthococcus Lagerstroemia).
What It Is
Crape myrtle bark scale is a sap-feeding insect that lives on the bark of some plants, especially crape myrtles (Lagerstroemia species). They secrete a sugary substance called honeydew that results in a black mold on the branches and trunk. Although the scale will not kill the plant it can result in stunted growth and reduced flowering and the black mold is certainly unsightly. Also, honeydew attracts ants (Merchant).
- To remove the black mold wash the trunk and branches with a weak solution of water and dish soap with a large brush like the type used to wash a car (Laminack).
- While the tree is dormant during the winter spray the trunk and branches with dormant oil to smother overwintering scale insects (Laminack). Dormant oil is highly refined mineral oil and is eco-friendly.
- To get ahead of the pests next year apply a drench type systemic pesticide in mid-March. The systemic pesticide should contain imidacloprid or dinotefuran (Williams).
- If you continue to have issues during the spring and summer the trees should be treated with a contact insecticide spray that contains the active ingredient Bifenthrin. A second treatment may need to be applied 2 weeks later (Williams).
Here are a few tips for healthy and beautifully blooming crape myrtles next season:
Planting (Collin County Master Gardeners)
- Choose a variety of crape myrtle that will grow to a suitable width and height for the location.
- Plant your trees in well-drained soil with full sun exposure, at least 6 hours daily.
- Dig a hole two times wider than the root ball. The tree’s root crown should be no deeper than the depth it was in the container or slightly higher than the surrounding soil. Backfill with the same soil that was removed from the hole; do not add amendments such as fertilizer or compost.
- Water thoroughly after planting. Add a 3” to 5” layer of mulch in the root zone leaving a 2” to 4” gap between the mulch and the tree’s trunk.
Fertilizing (Dr. Jerry Parsons)
- In early spring apply a complete slow-release fertilizer (N, P, K 19-5-9) at the rate of 2 pounds per 1000 feet of the branch spread of the tree.
- Make a second application in late fall.
Watering (Collin County Master Gardeners)
- Newly planted trees should be deeply watered 2 inches once a week in the absence of rain for the first couple of months.
- Crape myrtles are drought tolerant. Established trees should be deeply watered 2 inches once a month. The weekly light watering applied to your lawn grass is not adequate.
Pruning (Collin County Master Gardeners)
- Be selective when pruning to remove only broken branches or crowded growth in late winter or early spring.
- Pruning encourages new growth so avoid pruning in early fall before the first frost which can result in freeze damage to the new growth.
- Remove suckers that grow at the base of the tree at any time.
- Remove spent blooms to encourage reblooming.
Sources and Resources
Laminack, Janet. “Crape Myrtle Bark Scale.” DCMGA.com, Denton County Master Gardener Association, 21 Dec. 2016, youtu.be/lbFPSWEJhvc.
Merchant, Mike. “How to Treat Your Crape Myrtle for Bark Scale.” citybugs.tamu.edu, Texas A&M AgriLife Extension, Insects in the City, 28 Aug. 2018, citybugs.tamu.edu/2018/08/28/how-to-treat-your-crapemyrtle-for-bark-scale/
Williams, Rob. “Crape Myrtle Bark Scale Study Reveals Tree Treatments to Fight Pest.” https://ipm.tamu.edu/,Texas A&M AgriLife Extension, Texas IPM Program, 10 Mar. 2017, ipm.tamu.edu/2017/03/crape-myrtle-bark-scale-study-reveals-tree-treatments-to-fight-pest/.
Parsons, Ph.D., Jerry. “Crape myrtle -The Perfect Texas Landscape Plant.” https://bexar-tx.tamu.edu/, Texas A&M AgriLife Extension, Extension Education in Bexar County, 4 Sep. 2005, bexar-tx.tamu.edu/homehort/archives-of-weekly-articles-davids-plant-of-the-week/crapemyrtle-the-perfect-texas-landscape-plant/.
Question: My bearded irises didn’t bloom very well this year, so I guess they need to be divided. Could you give step-by-step instructions for dividing and replanting?
Answer: With rather showy blooms, the bearded iris might appear to be a garden diva, needing more attention than a pop star in decline. Granted, digging and dividing every three to five years demands a toll, but these drought-tolerant beauties offer a return much greater than the investment. Read on for step-by-step instructions and links for further research.
Timing and frequency of division
* Divide every three to five years or when blooming diminishes.
* In North Texas, divide in August or September. Blooming is complete, but there’s still time to establish a new root system before winter.
* Do not dig your irises in rain-saturated soil, which will become overly compacted if you do. Wait a few days after heavy rain.
* Before digging, cut leaves down by one-third of full height.
* Use spading fork to lift the entire clump. If you use a shovel instead, avoid getting too close to the clump so you don’t damage rhizomes or roots. Shake soil off the clump or use a strong jet of water to rinse off the soil.
Dealing with old or diseased rhizomes
* Remove rhizomes with borer damage and those that are soft or appear diseased. Put in regular garbage. Sterilize any tools that came into contact with the diseased plants in a 10% bleach solution.
* Remove aging rhizomes that look like leather or cork; usually, these old growths will not produce again. Do not compost iris bulbs.
Separating healthy rhizomes
* Separate the remaining, newer rhizomes. Each divided clump must have a “fan” of four to five leaves, at least a few inches of rhizome, and some healthy, white roots. Label the fans with permanent marker to more easily identify the varieties later.
* Place these newly separated clumps into a bucket with a 10% bleach solution for a few minutes while you amend the existing planting hole.
Amending the soil and fertilization schedule
*Amend the existing site with compost, mixing well. Some recommend using superphosphate in the amendments, but north Texas soil is generally high in phosphorous, so it is probably unnecessary. Withhold fertilizer until early spring, then use a lower nitrogen product, 5-10-5 or 6-10-10. Repeat fertilization after blooming and in late fall.
* To plant, form a mound of soil in the planting hole so that the top of the mound is about one inch below the top of the bed. Place the rhizomes on the mound with the roots extending down the sides and into the hole. Read the links below to learn how the angle of the fans and placement of the rhizomes impact the growth pattern and the overall design.
* Backfill carefully, covering the roots first and compacting the soil into place. You may need to hold the rhizome while backfilling so it remains at nearly ground level. Continue backfilling until the soil covers all the roots and one-half of the rhizome. Compact the soil gently, but firmly.
* Thoroughly water-in the transplants. Keep moist for the first two weeks as the plant establishes its root system, but do not allow standing water. Once established, irises need little water. If overwatered, the rhizomes will rot.
Mulching (Don’t do it!)
* Do not mulch the exposed rhizome. Covering the fleshy stem encourages rot and disease.
QUESTION: I love to see my neighbor’s daffodils bloom in late winter, but then I kick myself for not planting my own bulbs soon enough. When should I plant spring-flowering bulbs, and what low maintenance choices do you recommend?
Answer: By late winter, many of us yearn for the first glimpse of a bright daffodil. Bulbs require planning and patience, but thankfully, you’re not too late this year. Since it’s too hot to garden at the moment, plan your design and order desired bulbs in the next month or so for the best selection.
The broad term “bulb” describes plants that store most or part of their lifecycle within an underground, fleshy structure. Bulbs planted in the fall spend months growing the root structure necessary to sustain the showy flowers that cheer us in the doldrums of winter. Once blooming finishes, the leaves continue photosynthesis, storing nutrients in the bulb for next year’s blooms. As the leaves yellow and fade, we know it’s time to prune and await next year’s showing.
Most gardeners prefer perennial bulbs, which respond to our climate by continuing to bloom for a number of years before needing to be divided and shared. In north Texas, spring-blooming examples include daffodil/narcissus, grape hyacinth, and allium, among others. In the ever popular “tulip” category, look for “species tulips” that naturalize in north Texas, as opposed to the more widely known hybrid tulips that demand higher maintenance.
Plant bulbs when soil temperatures reach about 55 degrees. Planting too soon triggers leaf growth before a root system develops. Underground bulbs withstand freezing weather, but premature leaf growth succumbs to the same temperatures. Planting a little late is better than planting too early or, worse yet, saving the bulbs until the following year. If you order bulbs early, store them in a refrigerator away from any methane-producing fruits or vegetables until planting; do not allow them to freeze.
Question: My flower beds look straggly and worn from summer’s heat. What shrubs and flowering plants are safe to “clean up” now and what should I leave for later?
Answer: Mid-summer deadheading and light shearing revives flowering plants to generate a late summer flush of new growth. Even a light pruning of berry canes or removal of dead branches in woody ornamentals is helpful. The keyword is “light”; heavy pruning this time of year is not recommended.
First, let’s define terms. Deadheading entails the removal of spent flower heads and stems down to the nearest leaves; don’t just pull off the petals. Plants commonly deadheaded include daylilies, coneflowers and roses. Light shearing involves the mass removal of the top few inches of the plant, or down to the bulk of the foliage. This trimming is best for plants with small flowers closely spaced, like salvia Greggii, coreopsis and dianthus. Pinching back is the hand-removal of branch tips just above a leaf joint. This simple step encourages the emergence of side shoots, making a bushier plant. Coleus, marigolds and basil benefit from pinching back.
- Shrubs, annuals and perennials that bloom before mid-June are considered “spring flowering,” and they should have already been pruned. If you missed trimming them, just wait until next spring. If you prune them now, you may remove foliage necessary for next year’s blooms.
- Prune, deadhead, lightly shear and pinch back plants that began flowering this summer (after mid-June).
- Roses shouldn’t be pruned now, but definitely deadhead spent blooms.
- Avoid removing emerging buds.
- Never trim drought-stressed plants; make sure to prune after rainfall or irrigation.
- Wear garden gloves and watch out for paper wasps, asps and other pests nesting in your plants.
- Clean pruning tools between cuts on diseased plants. Use 70% rubbing alcohol. Don’t use bleach.
When to prune flowering shrubs and which to avoid pruning in summer: https://aggie-horticulture.tamu.edu
Details on pinching back: https://ucanr.edu
“Pruning, Demystified” https://www.provenwinners.com
Question: What shrubs can I plant to attract butterflies in Denton County?
Answer: Fall is a good time of year to plant shrubs, so this is a timely question. The survival rate to adulthood is only about 5 in 500 butterfly eggs. There are many reasons for this, but a big one is spraying for insects. If you are serious about butterfly gardening, you should forego pesticides.
Abelia, agarita, barberry, spirea, Texas sage, sumac, and Texas honeysuckle are all good shrubs for nectar. But of course, you must also plant host plants for the females to lay their eggs and for the larvae to eat. One of our Texas Master Naturalist friends compiled a list of host plants and nectar sources for 21 butterflies common in our area. Don’t you love when someone has done the work for you? It is a very helpful article.
For a complete list of native and adapted butterfly plants, go to Texas Smartscape. If you scroll down to “wildlife value,” one of the options is “butterflies.” You can input as many parameters as desired.
Question: My plants look fried. I’m not at all sure I’m watering enough for this heat. Can you give me some guidance?
Answer: North Texas’ often extremely hot summers can be hard on many plants. Knowing when and how much to irrigate grass, trees, vegetable garden, and flower beds can help. Don’t forget to add mulch to retain moisture and moderate temperature of the soil. AgriLife offers this advice on the most effective ways to add supplemental water.
Some plants are better able to take the heat than others. After our last terrible drought year in 2011, we surveyed our members to find out what thrived, what survived, and what died. You might want to look at that list for future planting.
Question: When should I fertilize my roses?
Answer: Roses should be fertilized around the middle of February—Valentine’s Day is a good reminder. Begin spring fertilization right after you prune them. Roses are heavy feeders, so continue to feed them every month during the growing season using a balanced fertilizer, e.g.10-10-10. (NOTE: Since our Denton County soil tends to retain phosphorus and potassium, it is recommended that you perform a soil test annually or every second year before adding more of those minerals.)
Question: My roses have black spot. Is there anything I can do?
Answer: This fungus is one of the most common rose diseases in the world. Unfortunately, if allowed to continue unchecked, your roses will become weak and susceptible to insects and other diseases. The best prevention is to look for black spot resistant rose varieties.
When leaves remain wet for 7+ hours, the fungus germinates, and splashing water spreads the spores to other leaves and canes. Since the disease depends on wet conditions, the heat of July and August inhibit the infection. Our typical wet, humid spring, however, is ideal for its spread.
If you can limit overhead watering, do so. If you do water with overhead sprinklers, do so in late morning so that the leaves will dry quickly. Remove the infected leaves and canes as soon as you see them. It is better to dispose of this material than to compost it.
The fungus survives the winter in fallen infested leaves. To minimize overwintering, collect and discard the diseased leaves in the fall and cover the area with mulch.
Fungi are hard to kill, so the goal is to control the infection as best you can. There are several fungicides (even some that are organic) that will help, but they must be used every 7-14 days. As we always caution, follow directions as stated on the label.
The following article contains more information about specific fungicides.
Question: Dozens of Cora vinca I planted in April are yellowing, wilting and dying! Could it be a fungus? I thought the Cora vincas were immune! What did I do wrong?
Answer: Oh, the heartbreak of vincas and fungus! I feel your pain and can help you sort it out.
First, what you did right: Selecting Cora series vinca! These Texas Superstar darlings emerged from years of trial garden study to address the chronic fungal issues of the vinca. The Cora series plants were named after Cora Van Wingerden – the matriarch of one of the most notable horticulture families in the US. With the steadfast character traits of their namesake, Cora vincas thrive in summer’s heat.
Now, let’s explore what went wrong. Early planting undoubtedly contributed to your troubles. These heat-loving annuals must not be planted before late May in Denton County. Unfortunately, the plants appear in garden centers in April, so we are tempted to plant early. Wait for late May, even June!
Next, we need to address immunity vs. resistance. These plants are NOT immune to fungal infection; they are RESISTANT. If environmental conditions favor fungal growth, even this new variety can succumb. As a preventive, use fungicides labeled for control of Pythium sp., Phytophthora sp., and Rhizoctonia sp. in vincas. Read labels completely and follow all instructions.
Poor irrigation and drainage contribute to the dreaded “f” word infestation. If using overhead sprinklers, water early so leaves dry by late morning. Drip irrigation is preferred. Use several inches of mulch to keep wet soil (and spores) from splashing onto leaves. With regard to drainage, vincas don’t tolerate “wet feet.” To sum up, they fare best with dry leaves and occasionally damp roots.
Next spring, do not plant any variety of vinca in the same beds. Research annuals that tolerate being planted earlier in spring and that are less susceptible to fungus. Use them in alternate years to the vincas.
Links for further reading:
- Disease ID and management:
- Earth Kind plant selector:
- History of Cora vinca development:
Question: Every spring, when monarch butterflies pass through Texas on their migration, I always wish my landscape had more plants helpful to them. Is it too late to plant milkweed? What varieties are best? I heard tropical milkweed can be a problem.
Answer: You’re not alone in your fascination with monarch migration and life cycle. To assist in this miracle of nature, plant only native milkweeds. Recommended varieties for north Texas:
Antelopehorn (A. asperula), Butterfly milkweed (A. tuberosa), Green antelopehorn (A. viridis), Zizotes (A. oenotheroides)
Although monarch butterflies enjoy nectar from many types of flowers, Monarch larvae feed exclusively on milkweed, so it must be available in spring when females lay eggs. To nourish both migrating butterflies and their offspring, incorporate other plants that flower in a staggered timetable so nectar is always available. Fall flowering plants are equally as important, since the final, migrating generation will need food sources for its journey south. Click here for info on Monarch Lifecycle
Ideally, native milkweed should be planted by March for spring migration. However, since milkweed is a perennial, go ahead and plant it. Although your new planting may not help this year’s migrating butterflies, it will give this year’s first-generation offspring a host plant for the second generation, and so on. Click here for info on Creating a Monarch Habitat
Conventional nurseries occasionally carry the native milkweeds; a better option might be to look for retail nurseries specializing in native plants. Scour local plant sales and ask fellow gardeners if they have some to share. Consider propagating your own once you have a supply. Alternatively, look for reputable mail-order sources. Click here for Native Seed Finder
Non-native, tropical milkweeds should not be planted. In more temperate climates, they may encourage year-round monarch colonies, which is undesirable for the species. Also, the long life of the native plant in warmer areas (San Antonio and southwards) can provide shelter to a protozoa harmful to the monarchs. If you already have a tropical milkweed in your garden, consider replacing it with a native. If you can’t bear to part with it, cut it back to a 6-inch stalk in the early fall and continue to trim new growth until winter causes dormancy. It will grow back in the spring. Click here for Risks of Growing Non-natives.
Question: I recently planted a Zuni crepe myrtle in mid-April. Now, a month later, I noticed some of the leaves are curling in a little and the edges are turning brown. What do I need to do to keep it from dying?
Answer: What a wonderful plant choice you’ve made! Zuni crepe myrtles have lovely lavender flower trusses, orange-red to maroon foliage in the fall, and attractive peeling bark. Your pictures and description indicate that your newly transplanted crepe myrtle is suffering from leaf scorch as a result of transplant shock. Not to worry, there are steps you can take to return your plant to health. Let’s walk through what transplant shock is, what the causes are, and the steps you can take to reverse it and avoid it in the future.
Transplant shock is a term that refers to a variety of stresses that occur in recently transplanted trees or shrubs. These stresses result in the plant struggling to root well and establish in the landscape. The symptoms of transplant shock can resemble those from plant diseases or insects.
- Dieback and/or thinning in the plant’s canopy
- Leaf scorch (brown edges) or brown leaf tips
- Premature fall color or early leaf drop
- Limited twig growth or limited flowering
- Delayed leafing out in the spring
- Excessive seeds or cones
- Diseases or insects
Because the plant is under stress, it is more susceptible to disease and insects may be suffering from both transplant shock and disease or insect infestation.
According to Kentucky Cooperative Extension and Penn State Extension, there a number of causes of transplant shock:
Poor plant material
- A plant species or cultivar that is not well suited to growing in North Texas
- The root ball dries out before transplanting in the landscape
- The leaves or twigs are damaged during transport due to wind or rough handling
- Container grown plant’s roots are root-bound or circling in the container
- Unhealthy plant to begin with
- The plant’s root ball is too small for the top growth of the plant
Bad planting location
- Poorly drained soil causing the plant to have “wet feet” where its roots are suffocated from too much water
- The soil is compacted
- A mismatch in the plant’s sun requirements, e.g., a shade lover planted in full sun or vice versa
Improper transplanting techniques
- The feeder roots are damaged during transplanting
- The planting hole is not the right size – too small, too deep (most common), too narrow
- The sides of the planting hole are “glazed” – slick and smooth caused by digging the hole – making it difficult for the new roots to penetrate the soil
- The packing / binding material such as twine, burlap, wire is not removed prior to planting
- Excessive fertilizer applied at the time of planting causing root burn
- Damage to the young bark from freezing temperatures or too much sun
Poor post-planting care / maintenance
- Improper watering – too much, too little, too frequent
- Application of too much nitrogen causing excessive top growth compared to root growth
- Mower or string-trimmer damage
The best strategy is prevention; however, these steps may help reverse transplant shock. Don’t expect a “miraculous recovery”; returning to a healthy state can take 3 to 5 years.
- Supplemental water is the single most important method for preventing transplant shock. Newly transplanted trees and shrubs do best with watering equivalent to 1 to 2 inches of rainfall each week. Water deeply once each week; do not sprinkle or apply small amounts of water frequently.
- Mulch the entire root zone 2 to 4 inches deep, leaving a gap of 4 to 6 inches between the mulch and the trunk.
- Remove dead or dying branches
- Have your soil tested to determine what nutrients may be missing. This link on the DCMGA website explains why soil analysis is important and provides the step-by-step instructions for getting one done: https://dcmga.com/north-texas-gardening/community-gardening/soil-testing/
- Fertilize after 1 year following the recommendations of the soil analysis. This will allow the plant to establish a healthy root system rather than growing leaf canopy.
- After the first season, remove the tree wrap
- If you believe the planting site is the culprit, relocate the plant to an appropriate site during its dormant season. To reduce the risk of transplant shock in this case, prune the roots several months to 1 year in advance, preferably in the fall. You can do this by cutting through the roots with a spade in a circle all around the plant just inside where you want the future root ball to be. This will encourage new feeder roots to develop.
To avoid transplant shock in the future, practice good transplant techniques:
- Select healthy plants suited to growing in North Texas. This link from Texas A&M AgriLife Extension lists the Top 100 Plants for North Texas to help you make smart plant purchases: https://agrilifeextension.tamu.edu/wp-content/uploads/2015/08/top-100-plants-for-north-texas.pdf
- Examine the plant before purchasing looking for circle roots (remove from the container), damaged limbs or bark, or evidence of diseases or insects.
- Plant relocated or nursery grown plants as soon as possible. Prepare the plants for transplanting by keeping bare-root or balled-and-burlapped plants moist until transplanting and soaking the roots 30 minutes before transplanting.
- Prepare the planting hole making it 2 times wider and the same depth as the root ball. Rough-up the sides of the planting hole and do not plant in soil that is soaking wet.
- Prepare the plant for transplanting by removing all packing and binding materials, remove dead or broken roots with sharp pruners.
- Spread the roots out in the planting hole, make sure the plant is resting at the same depth in the hole as the root ball with the root flare exposed, and backfill with the soil from the original hole.
Sources and Resources
Gauthier, Nicole; Kaiser, Cheryl; Klahr, Mike. “Transplant Shock: Disease or Cultural Problem?” plantpathology.ca.uky.edu, Kentucky Cooperative Extension, 1 May 2014, plantpathology.ca.uky.edu/files/ppfs-or-w-19.pdf.
Swackhammer, Emily; Sellmer, Jim. “Transplant or Moving Trees or Shrubs in the Landscape.” extension.psu.edu, Penn State Extension, 19 Oct. 2007, extension.psu.edu/transplanting-or-moving-trees-and-shrubs-in-the-landscape.
“Soil Testing.” dcmga.com, Denton County Master Gardener Association, 20 Jan. 2020, dcmga.com/north-texas-gardening/community-gardening/soil-testing/.
“AgriLife Water University’s Top 100 Plants for North Texas.” agrilifeextension.tamu.edu, Texas A&M AgriLife Extension, WaterUniversity, 1 Jan. 2015, agrilifeextension.tamu.edu/wp-content/uploads/2015/08/top-100-plants-for-north-texas.pdf
Question: The newest leaves on our live oaks are turning brown and dying. We also have a ton of leaf drop. What is this, and how can I treat it?
Answer: Cool, spring weather coaxes to life a pesky fungus called Taphrina caerulescens, commonly known as oak leaf blister. Affected oak leaves become deformed with bulges and twists. They develop yellow spots that eventually turn brown and feel papery. Sometimes, you’ll notice heavy leaf drop; other times, the diseased leaves remain on the tree. Also, in spring, live oaks experience natural leaf drop, which contributes to our impression that the disease alone is causing excessive leaf loss, when it is actually a combination of the two.
An unsightly condition, oak leaf blister rarely harms otherwise healthy trees. No fungicidal treatment is needed, unless your tree has lost a significant amount of leaves. Even then, it is too late this year to manage chemically. To prevent the problem from returning next spring, apply a recommended fungicide in late winter, just prior to bud break (late February). Treat again as soon as new leaves appear. Two or three weeks later, spray one more time. This preventive fungicide should protect the young and most vulnerable leaves during the cool, wet weather favored by the fungus. Mature leaves are not affected by oak leaf blister. Again, most trees will not require this intervention, only those with severe defoliation.
Do not trim infected leaves from the tree. Oak trees pruned between Feb. 1-July 1 may be susceptible to a fatal disease called oak wilt, which is spread by beetles active during this time window. Rather, simply rake up and dispose of all fallen leaves to lessen the fungal presence. Then, put it on your calendar to start fungicide treatments late next winter. If the trees are too large for you to treat, contact a certified arborist in your area for assistance. Many will make a free site visit to give you a quote; others charge a trip fee for the estimate. Make sure to ask.
For those trees most affected by the fungus, make sure to guard against further stressors. For example, provide proper irrigation this spring and summer (one inch every 7-10 days). Look closely for the presence of pests or other diseases, and intervene as recommended by science-based sources, like Texas A&M and other US land-grant universities.
Locally, the Denton County Master Gardener Help Desk is a free service staffed by well-trained volunteers. Reach out via e-mail at firstname.lastname@example.org or by phone at (940) 349-2892. Alternatively, access the free Cooperative Extension web resource called “Ask an Expert” at https://ask.extension.org/ask. For those who prefer audio learning, the Texas A&M Forest Service offers a weekly podcast entitled Trees Are Key, hosted by Paul Johnson, the Urban and Community Forestry Coordinator for the Texas A&M Forestry Service. Use this link to listen to the podcast: https://tfsweb.tamu.edu/podcasts/treesarekey/
Use the links, below, to learn more about oak leaf blister and proper tree care.
Oak leaf blister overview, including recommended fungicides: http://agrilife.org/plantclinic
This article mentions where new buds will emerge on the branches and includes a labeled picture. Look for the photo captioned “New buds on live oaks”: https://plantclinic.tamu.edu/factsheets
Find a certified arborist near you: https://www.treesaregood.org/findanarborist
This link gives reasons for hiring an arborist and lists their scope of work: https://agrilife.org/treecarekit
USDA’s tree owner’s manual is an excellent resource: https://www.fs.usda.gov
Question: Virginia creeper and poison ivy grow together on our property. In spring, the new Virginia creeper sometimes displays a three-leaf pattern similar to PI. How can I tell the difference between them, and how can I treat the PI without harming desirable plants?
Answer: Spring warmth awakens our garden favorites, but it also coaxes to life the undesirables, like poison ivy. The chameleon of vines, PI varies greatly in its appearance, confounding our efforts to identify and avoid it.
Read on to learn the differentiating characteristics and control measures. Links, below, allow for further research. There’s even a fun quiz to help you practice PI identification. This author got 53 correct out of 55. Who can beat that score? Comment below!
Virginia creeper – Each compound leaf consists of UP TO five leaflets. In early growth, VC may only
show 3 leaflets, with more leaflets appearing over time.
PI – Center leaflet has a longer stalk than the side leaflets, which seem to have almost no stalk at all and are always directly opposite each other.
VC – Individual leaflets radiate uniformly from the center with virtually equal stalk lengths.
PI – Has no tendrils or adhesive discs, but uses aerial roots to climb structures.
VC – Uses tendrils and adhesive discs to climb structures.
PI – Older vines have a demonstrable hairy appearance due to the aerial roots. Evidence of old, hairy vines wrapped around a tree, for example, will signal that PI was or is present in the area. These old vines contain the same irritating chemical as the rest of the plant.
PI – Off-white berries in clusters form in spring and remain all winter.
VC – Greenish spring blooms produce berries that ripen to a black or dark blue in the late fall.
PI – Leaf margin appearance varies greatly.
VC – Leaf margins are serrated.
Poison ivy, especially when immature, can be pulled—or “grubbed”—when the soil is moist. To protect your skin, wear gloves, a long-sleeved shirt, and long pants tucked into socks. Place a plastic bag over your hand and forearm; then, grab pliers with your “bagged” hand and pull up the vine from ground level (you want as much of the roots as you can get). The bag can be inverted over the vine for disposal. Your pliers will have to be washed after grubbing, as the PI skin irritant can be transferred from the tool to you. Your clothes must be carefully removed and washed, for the same reason.
An effective chemical method of control involves cutting the PI vine and immediately brushing the open cut with an herbicide labeled for PI. A dishwashing wand-type applicator with a sponge tip is a great tool for this job. (Reserve this sponge for herbicide use only.) Use an empty can to carry a small amount of herbicide and the sponge-wand as you go about searching for these persistent vines. Dispose of remaining herbicide as recommended on the product label. Sponge application is safer than spraying, since you won’t need to worry about overspray reaching desirable plants. Always wear the personal protective equipment as directed on the herbicide label and follow all usage instructions.
You may have to treat repeatedly to control PI, but it can be managed.
Remember to take the PI quiz so you will be better able to outwit that wily, garden chameleon!
Poison ivy identifying quiz (fun AND educational): https://www.birdandmoon.com/poisonivy/
Poison ivy control: https://aggie-horticulture.tamu.edu/travis
Distinguishing between poison ivy and Virginia creeper: https://extension.umd.edu
Great article on distinguishing between poison ivy and look-alikes https://www.canr.msu.edu/news
Helpful article describing Virginia creeper http://sfrc.ufl.edu/extension
Using pliers-and-bag method to pull PI: https://aggie-horticulture.tamu.edu/newsletters
Question: Last spring, the leaves of my live oaks were drying out and falling off. I thought it might be a fungus, so I sprayed them with a fungicide. Through the summer, the trees seemed to be okay. Two weeks ago, during one of our very windy days, I noticed hundreds of leaves blowing off our trees. I again sprayed them with fungicide, for lack of anything else to do at the time, and went to my computer to research my problem. The only thing I could find that matched my problem was Oak Wilt. (Some leaves have brown spots, but most are just brown.) Is there anything I can do for my trees, or must I replace them with some other kind of tree?
Answer: I believe what you’re observing is most likely normal spring leaf drop, but you were wise to make note of and investigate changes in your landscape.
Live oaks are considered evergreen trees, but they have a confusing leaf drop/replacement pattern that can be alarming. Healthy trees will have a heavy leaf drop spanning several weeks in spring. Throughout the rest of the growing season, you may notice some minimal leaf drop and replacement, which is also normal.
You may see another perplexing pattern in spring leaf drop, where one tree in your yard may start losing leaves weeks prior to your other trees. Again, this behavior is not uncommon nor any cause for concern.
During spring leaf drop, trees are never completely leafless, though they may have a sparse leaf distribution while the new buds emerge. If your trees are showing complete defoliation without evidence of emerging leaf buds, along with brittle twigs and branches, that would be of greater concern. In this case, I would recommend contacting a certified arborist near you for an on-site diagnosis. I will include a link below to help you find a local certified arborist if needed:
If it is any comfort, oak wilt has not yet been observed in Denton County. If you remain concerned about oak wilt or other diseases, please submit a sample to the Texas A&M Plant Disease Diagnostic Laboratory for analysis. The standard analysis costs $35 and covers oak wilt, among other diseases. For a submittal, use the following form:
The articles below explain normal live oak growth, as well as the disease conditions common to live oaks in Texas. I hope the information will be helpful to you.
Question: There is a sap-like substance dripping from my live oak tree and dropping all over my car. It looks like the substance that drips from crape myrtle trees when they have aphids. What is causing this on my live oak and what can be done to stop it?
Answer: Your live oak tree is likely infested with either a scale insect (oak lecanium scale, Parthenolecanium quercifex) or an aphid insect (oak leaf aphid, Myzocallis spp.) Both insect pests produce a sticky substance called honeydew that will appear as dark splotches on the leaves and can result in a black sooty fungus.
Oak lecanium scale (Parthenolecanium quercifex) can often be found on oak trees. Check the leaves and twigs of your tree for small tortoise-shaped brown insects about .06 to .25 inches in diameter. In April and May females lay their eggs. After hatching, the immature scale insects suck sap from the leaves. The scale infestation can rapidly increase on urban trees or trees under stress. Serious infestations of lecanium scale can result in stunted growth, yellowing leaves, and premature leaf drop.
Oak Leaf Aphids
Oak leaf aphids can be found on the undersides of leaves, leaf stalks, and young twigs of trees in the red and white oak groups. They are .04 to .06 inches long, soft-bodied and pear-shaped. They can be yellow, green, pink or brown in color with dark stripes on their back. Oak leaf aphids feed on the underside of leaves. A heavy infestation can cause the leaves to curl and weaken the plant. The leaves will become sticky with honeydew which will be followed by black sooty fungus.
Beneficial insects such as ladybugs and parasitic wasps can often keep scale and aphid infestations in check. On small trees, you can scrape off the insects or blast the undersides of the leaves and twigs with a strong stream of water. In larger trees, it is not practical or safe for a homeowner to attempt to control the infestation by spraying an insecticide into the canopy of the tree. Applying a horticultural oil in the spring to smother the insects is somewhat safer. Some systemic insecticides labeled for these pests can be applied through the soil or bark. Always read and follow the product label instructions for safety and proper use.
We strongly recommend engaging a certified arborist to diagnose and treat your tree. The arborist will have the equipment and know-how to treat the tree’s canopy. To find a certified arborist that works in your area go to one of these links and enter your zip code: http://isatexas.com/for-the-public/find-an-arborist/
Sources and Resources
Williamson, Ph.D., Joey. “Oak Diseases & Insect Pests.” hgic.clemson.edu, Clemson Cooperative Extension. Home & Garden Information Center., 10 Jan. 2020, https://hgic.clemson.edu/factsheet/oak-diseases-insect-pests/.
Norton, Russ. “Trouble Maker of the Month: Oak Lecanium Scale.” ag.umass.edu, University of Massachusetts Amherst. The Center for Agriculture, Food and the Environment, 1 Jul. 2019, https://ag.umass.edu/landscape/newsletters/hort-notes/hort-notes-2019-vol-305.
Solomon, J.D.; McCracken, F.I.; Anderson, R.L.; Lewis, Jr. R.; Oliveria, F.L.; Filer, T.H.; Barry, P.J. “Oak Leaf Aphids (Myzocallis spp.).” wiki.bugwood.org, BugwoodWiki, 1 Jan. 1987, https://wiki.bugwood.org/Archive:Oak/Oak_Leaf_Aphids.
“Find a Texas Arborist Near You.” ISATexas.com, Texas Chapter: International Society of Arboriculture, isatexas.com/for-the-public/find-an-arborist/. Accessed 25 Jan. 2020.
“Find an Arborist.” treesaregood.org, International Society of Arboriculture, www.treesaregood.org/findanarborist/findanarborist. Accessed 25 Jan. 2020.
QUESTION: Our HOA wants to plant eastern redcedars as a windbreak around our neighborhood. I’m dreading the pollen and allergies it triggers. Could you suggest less allergenic trees or shrubs we could consider?
ANSWER: Oh, the scourge of “cedar fever” during our north Texas winters! Between the eastern redcedar common east of I-35 and ashes juniper west of I-35, we’re surrounded. To avoid adding to our “cedar fever” problem, simply choose FEMALE redcedar trees, which produce fruiting bodies, but no pollen.
To differentiate between male and female trees, look for purple fruit on the female trees and small brown cones on the ends of the male’s leaves. Conveniently for your HOA’s planting schedule, the trees are in full display at the moment, so it should be easy to make an accurate ID before planting.
Since you asked, a less-allergenic alternative to eastern redcedar (Juniperus virginiana) would be pinyon pine. the links below offer more information about choosing less allergenic plants for your neighborhood and yard:
Allergy-friendly gardening with supporting research-based data
Developer of the Ogren Plant Allergy Scale (OPALStm)™
Question: I have an issue with branches falling off an American Elm tree. They appear to have a circular cut through them. Can you tell me what is causing this?
Answer: Thank you for contacting the Denton County Master Gardener Association Help Desk. We’ve received several questions about this strange phenomenon. The culprit is twig girdler beetles (Oncideres cingulata).
Twig Girdler Beetles
Twig girdler beetles are found throughout Texas. There are three species common to Texas: pecan girdler, mesquite girdler and huisache girdler. The pecan girdler is the species common to North Texas. Despite its name, it hosts on a wide variety of tree species including elms.
The female girdler uses its mandibles to cut a notch in a living tree branch and chew around it until it is almost completely severed leaving a small amount of heartwood connecting the branch to the tree. She deposits eggs in that remaining heartwood and protects it with a secretion. When the larvae hatch they burrow just below the bark and feed on the deadwood of the branch. Most of the pecan girdlers mature and emerge as adult beetles from late August through early October. Some, however, do not mature and emerge until the late spring of the next year.
Most often the damage is noticed in the fall when the girdled branches break off from the tree due to wind or the weight of the branch. If there is a heavy infestation it’s not uncommon to see the ground under the tree covered in girdled branches. The good news is that they typically do not do serious harm and are not a threat to the tree’s health.
Options for Control
Texas A&M Forest Service and the Texas Agricultural Extension Service both recommend the following as the most effective control of twig girdlers:
● Collect all severed branches
○ Gather all the fallen branches from under the tree
○ Remove any severed branches that may be hanging from or lodged in the tree
○ Be sure to check nearby trees for fallen branches and collect them too
● Destroy the branches
○ Burn the collected branches if allowed in your area
○ If burning is not allowed, shred or cut up the collected branches and take to a sanitary landfill, do not compost or use as mulch
Insecticides are not recommended by either service except in the case of high-value young trees or in an orchard. In that situation, Texas Agricultural Extension Service recommends:
● For pecan trees use an insecticide that contains azinphosmethyl or EPN
● For ornamental trees use an insecticide that contains lindane or chlorpyrifos
● The insecticide should be applied when the adult beetles emerge typically in the first week of September and again in early October and early November
● As always, carefully read and follow the cautions and instructions on the product label.
Sources and Resources
TWIG GIRDLERS, Texas Agricultural Extension Service
FOREST HEALTH: TWIG GIRDLING BEETLES, Texas A&M Forest Service
Twig Girdler, Texas A&M AgriLife Extension
QUESTION: The bark on our Monterrey oaks are darkening at the base of the trunk, and the bark flakes off easily. The leaves look good, but this recent discoloration concerns us. The trees were planted six months ago. What is this, and how can we treat it?
ANSWER: Monterrey oaks (Quercus polymorpha) serve well in Texas landscapes as a native tree. But like all trees, they thrive best when given the right start. Your pictures show that several issues trouble your trees, but you might be able to save them with careful intervention. You’ll need a certified arborist to help you, and I will include a link to find a reputable, certified arborist near you. You’ll also find below six additional links for further research.
But first, let’s explore what caused the trouble and how to remedy it.
Problem 1: The most obvious issue is the mechanical damage to the bark, both from the original strapping used to bind the burlap around the root ball and from the equipment used during lawn care. Bacteria could have entered the trunk via this damage, causing what is referred to as “bacterial wetwood.” Your photos show girdled bark as well as missing bark, both of which can stress trees and cause an early demise. Arborists use a technique called “repair grafting” or “bridge grafting” to treat damaged bark. Ask your arborist if this method would be an option.
Problem 2: I also notice in the picture a bright green material circling the tree on the lowest visible edge of the trunk. Maybe nylon twine? Was the packing material (burlap or wire) removed fully from the root ball before planting? Sometimes homeowners believe the roots will just grow through the packaging. All those materials should have been removed before planting.
Problem 3: Your trees appear to be planted too deeply. Trees should be planted such that the root flare is easily visible above the soil line. (The root flare is the transition area between the trunk and the roots.) Since the flare consists of trunk tissue, it must not be covered by anything! Not mulch, soil, turf, landscape stones. Nothing. Proper planting protects the root flare and overall tree health. Ask the arborist about replanting the tree or otherwise exposing the root flare. Exposing the flare can be done yourself by hand or by an arborist using an air spade (often reserved for trees more established than yours.)
Solution 1: Contact a couple of certified arborists in your area for an on-site inspection and diagnosis. They replant the tree or expose the flare, treat the wetwood, if needed, and determine if bridge grafting will work for the bark damage. Most certified arborists will visit your property for free, so make sure to ask. Once you have the arborists’ opinions and estimates, you’ll be better equipped to make a decision on how to proceed.
Solution 2: The arborist may be able to help. If not, maybe your trees came with a warranty from the company that planted them or from the nursery, if you planted them yourself. It may be less expensive to replace these young trees than to treat them.
QUESTION: Our post oak’s leaves are spotted, discolored and are already dropping from the tree. Two arborists gave us conflicting diagnoses. One said it was root rot, but our tree is at the top of a hill, so rot seems unlikely. The other arborist said it was a fungus called Tubakia. What do you think, and what should we do?
ANSWER: Both of the arborists could be correct. On the issue of root rot, post oaks prefer well draining soil. They suffer from continuously wet soil as well as from wide fluctuations in moisture. However, since your tree is on a hill, “wet feet” is less likely, but wide variation in moisture is still a concern. You can use an inexpensive soil moisture meter to determine if your tree needs irrigation or if you should withhold watering for a time.
The Tubakia dryina fungus is a strong possibility. Typical in late summer/early fall, this fungal pathogen requires no chemical treatment. It will not kill your tree, but it is unsightly and may signal a stressed tree. To help prevent future infection, clear fallen leaves frequently. By removing the leaves, you will lessen the number of spores that can overwinter on your property and impact your tree next year. The leaves can be composted, but care should be taken to ensure that the temperature reaches 140 degrees to kill the fungus.
Stressed trees are more likely to succumb to disease. Think through what might have stressed your tree during the past few years.
* Irregular moisture? (Monitor with an inexpensive moisture meter and adjust irrigation, if possible.)
* Heavy clay soil that drains slowly? (Consider aerating the root zone and topdressing lightly with compost. Plunging a screwdriver fully into the ground every few inches should work to aerate; no need for an expensive process.)
* The root flare being covered by soil or mulch? (Gently clear away the soil/mulch from the trunk, exposing the flare. You can suffocate a tree by covering its root flare.)
* Lack of fertilization? (Have your soil tested; see below.)
Regular lawn fertilization should provide sufficient nutrients for your tree. However, if the tree doesn’t receive fertilization, you may want to send a soil sample to Texas A&M Soil Testing Laboratory to determine the soil’s pH and its percentage of nitrogen, phosphorous and potassium. The lab will give recommendations for the quantity of each nutrient, if necessary.
Refer to the links, below, for more information on Tubakia and tree care.
Tips on preventing future infection (start now)
Fertilization of woody ornamentals and trees (wait until late winter, if needed)
Soil analysis form (to determine if fertilization is necessary)
Question: I have 20-year-old red-tipped photinias along my fence line that have leaf spot and it appears to be spreading. We are having a pool installed soon and the shrubs will need to be cut back for the installation. I’d like to keep the privacy the photinias provide especially with a pool, but want to know if cutting them back is a good idea or should I replace them?
Answer: Thank you for contacting the Denton County Master Gardener Help Desk with your questions about red-tipped photinias (Photinia x fraseri). According to Dr. Jerry Parsons of Texas A&M AgriLife Extension red-tipped photinias are “the most commonly sold shrub and, by far, the most problem-prone shrub in Texas. This shrub is highly susceptible to Red Tip Leaf Spot and yellowing caused by iron chlorosis.” His recommendation, although with reservations, is to:
- apply a fungicide that contains Propiconazole while young leaves are developing and reapply as frequently as the label will allow (every 10 -14 days) until the leaves mature, then reapply as needed
- collect and destroy all infected leaf litter from below the plants
Dr. Parsons fully endorsed recommendation is to “eliminate the sickly red-tipped photinias as soon as possible and replace them with hollies.”
Given that the Red Tip Leaf Spot is spreading and the photinias will be severally stressed by cutting them back for the pool installation which will likely accelerate the disease spread, it probably makes sense to remove and replace them with a Texas native or adaptable shrub that is less prone to disease.
Fall is an excellent time to plant new shrubs in your landscape. When purchasing your plants, be sure to buy healthy, high-quality plants from a reputable seller. Review the plant’s information tag carefully for sun, soil and water requirements to ensure it’s right for the location you plan to plant it. Also, consider the size of the plants, particularly the mature width, to determine the number of plants you need. Follow the spacing requirements on the plant’s tag to ensure growing success.
Here are some evergreen hedge-type shrubs of similar size that are excellent for North Central Texas:
Glossy Abelia, (Abelia x grandiflora), ht. 6’, wd. 5’
Agarita [native], (Mahonia trifoliolata), ht. 6′, wd. 4′
Oakleaf Hydrangea, (Hydrangea quercifolia), ht. 6’, wd. 6’
*Texas Sage, (Leucophyllum frutescens), ht. 6’, wd. 5’
Pfitzer Juniper, (Juniperus chinensis var. chinensis ‘Pfitzerana’), ht. 6′, wd. 9′
*Cleyera, (Ternstroemia gymnanthera), ht. 6′, wd. 5′
*Nandina, (Nandina domestica), ht. 6′, wd. 4′
Dwarf Burford Holly, (Ilex cornuta ‘Burfordii Nana’), ht. 5′, wd. 3′
Bush Germander, Teucrium fruticans, ht. 5’, wd. 5’
(*) denotes those plant materials which are particularly outstanding for this area
- The planting hole should be the depth of the root ball and about 6” wider in diameter than the root ball.
- To allow for settling and drainage, place the shrub slightly above the surrounding soil level and rest the root ball on a solid foundation in the hole.
- Handle the shrub by the root ball, not the trunk or branches
- Fill the hole with the soil removed from the hole (tip: when digging the hole, place the soil on a large piece of cardboard or tarp to make it easier to scoop it up for back-filling the hole). Do not add any amendments to the soil used for backfilling the hole.
- Deeply water the root ball and surrounding soil at the time of planting, follow with a deep watering every 7 to 10 days.
- Wait until early spring to fertilize with half-strength fertilizer to avoid burning or damaging the root system.
- Add a layer of 4” to 6” of mulch over the root zone. Do not pile the mulch next to the trunk, rather, leave a 4” to 6” gap of bare soil around the trunk.
Sources and Resources
Texas A&M AgriLife Extension, “The Unbeatable Foes In the Garden”,
Question: Over 5 of our post oak trees died suddenly. The leaves turned orange very quickly. Should we be concerned about our other post oak trees dying? Should we have the trees that died removed?
Answer: The DCMGA Help Desk has received a significant number of calls in recent weeks about post oak trees dying in what appears to be a short period of time. Ms. Sheila McBride (TPDDL diagnostician) and Dr. David Appel, Extension Plant Pathologist with the Texas A&M AgriLife Extension Service, believe the “phenomenon of rapid decline of post oaks is a result of varying extremes of soil moisture (drought and/or drowning) leading to attack by root rots, cankers, and wood-boring insects.” “Post oaks are a type of white oak, which are very susceptible to site disruption and rapid environmental changes.” (Kathleen Phillips, AgriLife Today, September 20, 2016)
Root rot can develop as a result of saturated soils (poor internal soil drainage) resulting in inadequate oxygen diffusion to the tree’s root system. All of these problems were made worse by the historic drought of 2011 when the health of these trees was crippled to such an extent that they are still suffering today. The heavy rainfall during the spring of 2016 and again during the spring of 2019 followed by a very hot dry period combined with poorly drained soils are contributing to their demise.
Ms. McBride and Dr. Appel report being confident the cause of the death of post oaks is NOT oak wilt. Oak wilt targets primarily live oaks whereas this situation is impacting post oaks, which are very resistant to oak wilt.
Your best course of action is to contact a certified arborist as soon as possible. Discuss diagnosis, treatment, dead tree removal and ongoing care and maintenance of your post oaks with the arborist.
In the meantime, maintaining even soil moisture availability in and around the remaining intact root system will assist in tree recovery. In the absence of rain, water deeply applying two inches once a month to encourage deeper rooting of your trees. Apply soluble high phosphorus and high potassium fertilizer into the root zone to supply developing roots. Do not prune or remove dead limbs from the trees while they’re under stress, rather, wait until they’re dormant.
Texas A&M AgriLife Extension, “The Care and Feeding of Post Oaks”
International Society of Arboriculture, Find an Arborist
Answer: Most of us enjoy garden discoveries, but finding tree damage never makes the happy list.
In your case, we can be thankful that you discovered the damage before it resulted in a more dire outcome. Let’s explore what went wrong with your magnolia, how to manage it, and recommended tree care, in general.
Your magnolia was probably the victim of a fungus that rotted the heartwood, creating a weakened trunk. Damage that low to the ground could make your tree more inclined to topple in high winds. You also may need to treat the area for fungus, as the spores can remain in the soil for years. But to know for sure, I would recommend consulting a certified arborist for an on-site diagnosis. The International Society of Arboricultural is the certifying agency for arborists in the US, and their website contains a search engine allowing you to find a certified arborist near you. (Link below)
We need to inspect our trees twice yearly, in the winter to detect structural defects and in the late summer, when it’s easier to notice dead branches and fungal infestation. Check tree structure after severe storms, as cracked branches may pose a safety hazard days or even weeks after the storm. During every inspection, look at the tree’s crown, branches, trunk and root areas. If you find signs of disease or damage, have a certified arborist inspect your trees. Even if your trees seem healthy, consult a certified arborist once every 3 to 5 years for a professional opinion. Many certified arborists will make on-site assessments for free. If work is recommended, get more than one estimate.
As the most valuable landscape element, trees require more attention than we might expect. Often, we fiddle with pretty annuals or favorite vegetables, forgetting that many trees have a lifespan far longer than ours, and deserve their own special care. Perhaps, tending to our trees will help grow our list of happy garden discoveries.
Homeowner’s guide to tree care: http://www.treesaregood.org/treeowner
Detecting tree problems: https://dcmga.com/north-texas-gardening/trees/whats-wrong-with-my-tree/
Value of tree inspections and method: https://www.purdue.edu/fnr/extension/why-tree-inspections/
Why hire a certified arborist: http://www.treesaregood.org/portals/0/docs/treecare/hire_arborist.pdf
Find a local, certified arborist: http://www.treesaregood.org/findanarborist/findanarborist
HELP DESK VOLUNTEER TURNS DETECTIVE
Answer: I am happy to help explore what’s going on with your holly, but first, consider this advice given by Dr. Theodore Woodward, professor at the University of Maryland School of Medicine, to his medical interns in the 1940s: “When you hear hoofbeats, think of horses not zebras.” This good advice can also guide us when confronted with a garden mystery.
Let me explain.
When I first saw the pictures of your holly, I was flummoxed. Stumped, if you’ll pardon the pun. Research turned up precisely nothing. Too embarrassed to admit defeat, I did what every self-respecting Help Desk volunteer would do: Marched right out to my own Nellie Stevens holly in hopes of finding the same “mulch.” Looking quite like Inspector Clouseau on a case, I dove head first into the shrub. Spiders, leaf spots, bugs, webs, stuff. And BAM: mulch!! Well, not mulch, but something that looked just like the substance on your holly!
There I was, head in the shrubs and neighbors side-eyeing me, when I realized that a harvest was in order. I carefully gathered the crumbly substance. Still not sure of its identity, I brought it inside for a closer look. A quick examination brought me to a somewhat underwhelming conclusion. The “mulch” was simply spent flower blooms from earlier in spring. Having fallen into the space between the leaves and the stems, the spent blooms remained there, decomposing for weeks. This plant debris was an absolute eyesore, but it was not a plant killer. Suspect #1 eliminated.
One mystery solved, there still remained the question of what killed your other holly. Unfortunately, you didn’t have photographs or specimens of the dead shrub, so I had no clues to lead research. In the future, take photos of the shrub in its entirety and closeups of its leaves or problem areas. Make notes of the age of the shrub, its location in your yard, watering history, most recent fertilization and pruning history, etc. Enclose plant samples in a labeled, resealable bag. Bring them to the Denton Agrilife office for a free, visual diagnosis or send them to the Texas Plant Disease Diagnostic Laboratory in College Station for lab analysis.
The metaphor may be a stretch, but hopefully, it will help in the future when you find yourself looking for zebras when the guilty party is actually a horse.
DCMGA Contact information: https://dcmga.com/contact/
Texas Plant Disease Diagnostic Laboratory website: https://plantclinic.tamu.edu/
Question: My large oak tree has split at the trunk. It is close to my house. What are my options? (See photo below, courtesy of DCMGA member Tracy D.)
Answer: This is a question that a certified arborist will need to evaluate. It looks like your tree has two dominant trunks, which causes the tree to be weak where they meet. High wind can then cause cracks or complete failure.
In general, your options are to cable it or cut it down. Cabling uses a cable and braces to add tension between the two stems to keep it from splitting. If it is a hazard to your house, then don’t delay in contacting a professional. Cabling is not something a homeowner should attempt, and neither is cutting down a large tree.
Look for a certified arborist with Tree Risk Assessment Qualification (TRAQ) to assess your tree and make recommendations for possible treatment. Here is more information from the Texas Forest Service.
Question: I planted two pecan seeds about 15 years ago. They have yet to produce a pecan. What am I doing wrong?
Answer: There are several reasons pecans don’t produce.
• Trees grown from seeds are slower to bear nuts. It may take 15 years.
• It could be a poor variety for pecan production.
• If you have clay soil, the tree will struggle. They prefer sandy loam.
• Your tree probably needs fertilizer. Inadequate zinc, nitrogen and lime can limit production. Get a soil test so that you will know for certain what your soil needs (soiltesting.tamu.edu).
• Poor pollination is a common reason for lack of nut production. Pecans produce both male catkins and female flowers on the same tree. However, frequently the catkin’s pollen is shed either too early or too late to pollinate the flower. Having more than one tree can help with this.
• Too much or too little water affects production.
• Disease and insect pests can seriously limit production. Look for a variety with good disease resistance. You can find a list here.
To learn more, read this article from the North Carolina Cooperative Extension.
Question: I wanted to plant an Empress tree but I was told that it is an invasive species. Can you tell me what that means? The tree is beautiful. Should I really care?
Answer: The tree you mentioned is a survivor. It can regenerate after it has been cut down, burned, or bulldozed. But it doesn’t just survive; it thrives. Producing up to 20 million seeds a year, it reproduces prolifically. Is that a bad thing? Yes, because we live in a fragile ecosystem that can be disrupted. The problem with invasive species is that they can outcompete native plants and prevent them from surviving.
Invasive plants have negative ecological, environmental, and economic consequences.
A healthy and diverse plant community consists of a variety of herbs, shrubs and trees. Invasive non-native plants, having few predators, can outcompete and displace native flora that are necessary food or cover for native wildlife. Or, the loss of diversity may reduce the quality of habitat for fish and wildlife so that they become weak or even extinct. Japanese knotweed and kudzu, for example, may displace all other forms of vegetation, creating a monoculture.
Large monoculture areas are more likely to erode during flooding than areas with a diversity of plants because there is less root structure to hold the soil in place. Excess erosion releases sediments to streams, leading to a degradation of water quality.
Monocultures can also create fuel for wildfires. For example, English ivy growing up a tree to the canopy allows fire to reach the top of trees, which makes the fire harder to control. Some invasive grasses become dry and dormant in summer, making them a fire hazard.
Some estimates are that invasive species cost as much as $120 billion per year in lost crop and agriculture production, removal costs, and reduced export potential. In other words, farmers pass along the cost of controlling invasive species by increasing the cost you pay for vegetables or meat.
Our suggestion is to search for a native tree of similar size and beauty. Here is a great list from the Missouri Botanical Garden.
Question: Some of my trees are already dropping leaves. Why is this happening? Should I be worried?
Answer: The trees are responding to heat and drought stress. Some may put on more new leaves in spring than they can support with available soil moisture. Some trees, our native cedar elm, for instance, are usually first to begin dropping leaves in August. This year they started in July. Others may go dormant in summer.
If all the leaves suddenly turn brown and remain attached to the tree, your tree may be dead. Check the twigs and buds. If the twigs are supple and the buds look normal, the tree is still alive. It is, however, a sign of stress. Next spring you will know for sure.
Do water your trees during the intense heat and frequent dry spells we experience in Denton County. If you must pick a priority to irrigate, let it be your trees. The time it takes to grow a mature tree, as well as their expense, make them much more valuable than grass or flowers. Read details here: https://dcmga.com/north-texas-garden…/trees/tree-irrigation/
Question: What is making these holes in a tree? Could it be borers?
Answer: Not borers but a hungry sapsucker. The damage is distinctive because the holes are close together in rows. Borer holes are randomly located, and usually, there are fewer of them. For more information about woodpeckers and possible control methods, check out this woodpecker publication from AgriLife’s Texas Wildlife Services. Photo credit: Chris Hayes, University of Illinois, Forestryimages.org
Question: One of my favorite old trees has ice damage. Can it be saved?
Answer: People have emotional attachments to their trees, and of course, you want to save it. However, there is no simple answer. First, it could be dangerous. If there are power lines down, or major branches hanging overhead, stay away. Also, if climbing or extensive chainsaw work is involved, leave it to the professionals. Look for a certified arborist at isa-arbor.com.
If the tree was generally healthy and thriving before the storm, it may recover, depending on the extent of the damage. It will depend on how much of the crown (foliage and branches) is intact, how big the wounds are, how much bark is damaged, and maybe even how much you want to save the tree.
For minor damage, prune the damaged limb(s) and wait to see if the tree recovers. Major damage usually cannot be repaired and the tree should be considered a loss. Two websites with additional helpful information are Texas Forest Service “Can my tree be saved” and Texas A&M AgriLife, “Proper Pruning Techniques”.
Question: My tree has what looks like a large mushroom about midway up the trunk. Should I cut it off?
Answer: Unfortunately, shelf mushrooms can be indicative of internal rot. Call a certified arborist to diagnose the tree and advise whether the tree might be a danger to your home. Find an arborist in your area by going to the International Society of Arboriculture Arborist Search page. You can input your zip code to find an arborist in your area.
Question: Can you tell me how to plant a tree properly?
Answer: Dig a hole about 2-3 times the diameter of the root ball. It is not necessary to amend the soil. If you are planting a container-grown tree, look at the roots to be sure they are not girdling the container. If they are, gently pull them free and spread them into the hole so that they will grow downward rather than in a circle. Plant the tree at the same level it was in the pot. If the tree is balled and burlapped, remove all ties and as much burlap as possible. You do not want anything to constrict the growth of the roots. Fill the hole with the same soil you removed. Be sure not to plant the tree too deeply. The top of the flare of the roots should be visible. Keep grass at least 2-3 feet from the tree trunk so that the tree does not have to compete with the grass for water and nutrients. Add about 2-3 inches of mulch, but keep it about a foot from the trunk. Remember, mulch is to moderate soil temperature and retard weeds. Regardless of what you see when you’re driving around town, mulch should never be placed against the trunk of the tree. The tree needs to breathe. Most trees do not need to be staked, but if you do stake it, leave the stakes no longer than one year. For a wonderful illustration of a properly planted tree, follow this link: Tree Planting
Question: When should I prune my peach tree?
Answer: If you can grow peaches in Denton County, you are a very good gardener. But if you are one of the lucky ones, there are specific instructions for pruning. Read the whole article here: Pruning peach tree
Question: When can I transplant a tree?
Answer: It is best for the tree if you wait until it is completely dormant (winter). If you are digging it up, be sure to get at least 1/2 the root area, or the tree will likely not survive. The roots extend at least as far as the drip line and sometimes much farther. Yes, that is a lot of digging. If the tree is several years old, the chances of survival are small because it is almost impossible to save enough roots for the tree to overcome transplant shock. Planting a small tree is a better idea.
Answer: This is damage from a twig girdler. Note the defined edge that has been eaten. The female lays an egg in the tip of the twig, chews the twig until it is damaged enough to die and fall off with the wind. Then the larva emerges to find a safe place underground to finish developing.
Question: What walnut varieties are recommended for North Texas?
Answer: Thomas or Carpathian.
Question: My well water is salty, and I am having trouble growing plants. What can I do?
Answer: First, look for salt-tolerant plants. Look at the list of Salt Tolerant Plants for the Texas Coast to get some ideas. Buy plants that require little water once they are established. A good place to start is with native plants. The goal is to get the plant established and then give it water as seldom as possible. Learn to appreciate the occasional deluge from tropical storms as this can help leach salts from the soil. You might also consider installing a rainwater harvesting system to use on your most prized plants that are salt-sensitive. Check out our Rainwater Harvesting page for more information.
What are these spots on my Indian hawthorn and how do I treat them?
These spots indicate infection with a fungus called entomosporium, which thrives on new plant growth following periods of rain in spring and fall when temperatures are 60-80 degrees. Entomosporium leaf spot is especially troublesome in Indian hawthorn and red-tip photinia, but other woody ornamentals in the rose family are vulnerable, as well. In fact, red-tip photinia are no longer recommended by Texas A&M Agrilife Extension due to the severe impact of entomosporium.
Thankfully, the pictures of your Indian hawthorn show minimal infection, so there’s hope. Help lessen the “fungal pressure” this spring using cultural control methods, below:
- Increase the airflow around the plant by pruning out excess foliage; however, do not prune away more than 1/3 of the plant.
- Rake away fallen leaves. These diseased leaves contain spores that can infect healthy foliage when rain or irrigation splashes the spores from the fallen leaves onto the healthy ones.
- Add mulch to a depth of three inches beneath the shrubs. Spores remaining in the soil can infect the healthy leaves via splashing, and the mulch will provide a barrier. However, do not allow the mulch to come into contact with the shrub’s trunk. A two-inch gap around the circumference of the trunk should be sufficient.
- Avoid overhead watering, if possible.
- Irrigate in the early morning, so any water left on the leaves can dry before nightfall.
- Below are steps to promote the health of your shrubs:
- First, complete the pruning, mulching and irrigation changes, listed above.
- Your shrubs should have been fertilized in late February or early March before new growth began. If you missed that window this year, simply proceed now with a second round of fertilization. A half-cup of fertilizer per square yard of foliage spread should be sufficient. Spread evenly over the root zone. Use a product with an N-P-K ratio of roughly 2-1-1 or 3-1-1.
- Do not fertilize the shrubs in the summer. The late-season growth promoted by summer fertilization will be more susceptible to entomosporium infection during cooler weather.
The Texas Plant Disease Diagnostic Laboratory at Texas A&M says that in otherwise healthy Indian hawthorn, entomosporium causes mostly cosmetic damage; however, after long-term exposure to the fungus, shrubs can succumb to the disease. The lab recommends treating with the fungicides thiophanate-methyl or myclobutanil on a schedule beginning in late fall/early winter and continuing through mid-spring. These fungicides are only effective as a preventative measure, so it is too late to use a fungicide now. Wait until late fall or early winter to begin treatment, then repeat applications once or twice monthly through mid-spring. Follow the labeled instructions regarding the timing and frequency of usage, as well as recommendations for personal protective equipment.
Disease overview: https://cdn-ext.agnet.tamu.edu
Read the section titled Pruning Shrubs: https://aggie-horticulture.tamu.edu
Read about the timing of fungicide application in the section titled Control: https://www.aces.edu/blog
Read about fertilizing shrubs: https://aggie-horticulture.tamu.edu/earthkind
Question: I found caterpillars devouring my canna lilies. Could you recommend an organic control method? How can I prevent infestation next year?
Answer: Canna lilies crown the garden with their impressive fronds and showy blooms. Attractive to gardeners for their beauty and heat tolerance, cannas also catch the attention of the diminutive Brazilian skipper butterfly who lays her eggs on the plants. Newly hatched larvae attach themselves to young, unfurling leaves, using silk to seal the leaf where they will feed until adulthood. Up to three generations of skippers hatch each year, and by summer’s end, the foraged leaves look tattered. It’s a grim ending to an otherwise illustrious garden gem.
Thankfully, several organic control methods exist to fight the battle with canna leafroller. For small stands of canna, destroying the pests by hand might be sufficient. You can squash them in their “shelters” or remove them to give to your chickens or fish. If you have only a small number of cannas, hand removal is probably best. Prune out any heavily infested leaves.
For large numbers of canna, the organic chemicals B.t. (Bacillus thuringiensis, variety “kurstaki”) or spinosad (pronounced spin OH sid) are more practical. Applied as foliar sprays, these products kill caterpillars which ingest treated leaves. The canna leaf possesses an impressive waxy layer, so make sure your product contains a sticker spreader or add one. Spray all surfaces, even drenching the interior of young leaf whorls. These products work best on very young caterpillars; apply as soon as you see infestation and as often as the label directs.
Throughout the season, prune all spent flower stalks since they do not rebloom. Cannas are prolific enough to put up new shoots rapidly, filling the gaps left from the pruning. In the fall, prune the entire bed to the ground and compost the debris. In doing so, you’ll remove most remaining eggs from your property.
Next May, look for evidence of leafrollers in new growth. Starting early with manual removal or chemical treatments will lessen the caterpillar damage all season long.
Life cycle information: https://texasinsects.tamu.edu
Photographs of leafroller eggs: http://entnemdept.ufl.edu
Fact sheet on B.t.: https://ag.umass.edu
Fact sheet on spinosad: https://aggie-horticulture.tamu.edu
Question: Tons of ornament-like growths are “decorating” my dying red cedars. What are the growths, how do I treat them and is there any hope for my trees? I spent a fortune on the trees for a windbreak, and I can’t afford to replant.
Answer: Bagworms have claimed your trees as their home. And their nursery. And their all-you-can-eat buffet. Fortunately, both Integrated Pest Management and chemical controls are effective this time of year, so read on and plan to act soon.
To help battle the problem, we should discuss the pest’s lifecycle. Usually, the first sign of an infestation is the distinctive, oblong “bags,” encrusted with plant debris, hanging from stems. The bags hold hundreds of eggs, which overwinter from the previous fall. Sometime between April and June, tiny larvae emerge, spin a single silk thread and attach themselves to nearby leaves where they begin feeding. The caterpillars use their silk and your plant debris to weave the case, which they carry and live in throughout the season, enlarging it to accommodate their growth. Male bagworms complete development as small moths, which emerge from the bags ready to mate. The female adult’s final stage is more maggot-like, without functional eyes, legs or antennae. She protrudes halfway out of her case and exudes pheromones to attract a mate. Once mated, she deposits her eggs into the case and dies. The eggs remain sheltered in the case until they hatch in spring when the cycle begins anew.
To get control of your infestation, hand-pick all cases from the tree AND the ground; discard in the regular trash. If your tree is large or infestation is severe, consider recommended chemical controls, even using a professional service for large trees. Timing insecticide usage to caterpillar lifecycle is critical. Insecticide is ONLY effective when bagworms are actively feeding in the larval or caterpillar stage. From about April to August is your insecticide window, but remember that any chemical control can impact beneficial organisms, so use as a last resort.
Recommended insecticides for early-season use include Bacillus thuringiensis, spinosad and any of the pyrethroid insecticides. Infestations noticed in late summer will require pyrethroid sprays for effective control. Before purchasing any insecticide, read the label fully to make sure the product is suitable for bagworms. Purchase any recommended personal protective equipment (PPE) you do not already own. Getting home without PPE may tempt you to use the product without the proper protection, and that is a risky action with any chemical.
Refer to the links below for detailed information from Texas A&M entomologists:
Question: Every spring, when monarch butterflies pass through Texas on their migration, I always wish my landscape had more plants helpful to them. Is it too late to plant milkweed? What varieties are best? I heard tropical milkweed can be a problem.
Answer: You’re not alone in your fascination with monarch migration and life cycle. To assist in this miracle of nature, plant only native milkweeds. Recommended varieties for north Texas:
Antelopehorn (A. asperula)
Butterfly milkweed (A. tuberosa)
Green antelopehorn (A. viridis)
Zizotes (A. oenotheroides)
Although monarch butterflies enjoy nectar from many types of flowers, Monarch larvae feed exclusively on milkweed, so it must be available in spring when females lay eggs. To nourish both migrating butterflies and their offspring, incorporate other plants that flower in a staggered timetable so nectar is always available. Fall flowering plants are equally as important since the final, migrating generation will need food sources for its journey south.
Ideally, native milkweed should be planted by March for spring migration. However, since milkweed is a perennial, go ahead and plant it. Although your new planting may not help this year’s migrating butterflies, it will give this year’s first-generation offspring a host plant for the second generation, and so on.
Conventional nurseries occasionally carry the native milkweeds; a better option might be to look for retail nurseries specializing in native plants. Scour local plant sales and ask fellow gardeners if they have some to share. (More info at dcmga.com) Consider propagating your own once you have a supply. Alternatively, look for reputable mail-order sources.
Non-native, tropical milkweeds should not be planted. In more temperate climates, they may encourage year-round monarch colonies, which is undesirable for the species. Also, the long life of the native plant in warmer areas (San Antonio and southwards) can provide shelter to protozoa harmful to the monarchs. If you already have tropical milkweed in your garden, consider replacing it with a native. If you can’t bear to part with it, cut it back to a 6-inch stalk in the early fall and continue to trim new growth until winter causes dormancy. It will grow back in the spring.
Question: My yuccas are being destroyed by tiny bugs with a red head. What are they?
Answer: Those are yucca bugs. Pesticide applications should target nymphs because eggs are not affected. Determine this stage by looking for spiny nymphs near egg masses on leaf undersides and monitoring to determine egg hatch. Short residual materials, like soaps, oils, or pyrethrins, can be effective on nymphs if coverage is adequate. Systemic pesticides such as Orthene (Acephate) or Merit (imidacloprid) are also very effective. Topical foliar applied materials can also provide effective control.
Question: There is black stuff on my trees and many of my plants. It looks like mold.
Answer: It probably is sooty mold. This mold often grows on the honeydew (a sugary liquid waste) of insects such as aphids. Look for evidence of aphids on the backside of leaves. To the naked eye, they usually appear as tiny white dots.
Question: There is something that looks like vomit on my begonias.
Answer: That is a harmless slime mold, but it does look like a dog barfed in the flower bed. You can ignore or hose it away. If you kick it, you will likely get the spores all over your shoes.
Question: (March 2011) I used an herbicide on grass that I used to make hay for my horse. I have composted the horse manure for about six months. Is it safe to use the compost?
Answer: It depends on what herbicide you used. Some herbicides may persist in manure for many months or even years. There is a simple bioassay that homeowners can conduct to find out if their compost is safe. Directions and more information is in the following article from North Carolina State University.