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
Frequently Asked Question Categories
- Flowering Perennials
- Trees and Shrubs
- Water Conservation
- Insects, Diseases and Pests
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.
Detailed articles are linked below for your research, including a link on treating sandbur.
Best wishes in making improvements in your heritage farm.
Detailed article on overseeding, plugging and sodding, including soil prep and weed control
Detailed info on overseeding winter ryegrass
Article on Panterra ryegrass character traits
Details on Panterra ryegrass
Overview of buffalograss
Thorough article on weed control in warm-season grasses, like buffalograss
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.firstname.lastname@example.org. 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.
This tool helps you calculate exactly how much water you need based on grass type and current weather data.
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.
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.
Recommended variety: Natchez, a Texas Superstar™ (Note instructions for “pinching” to control growth, rather than intermittent in-season pruning)
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 Texas Winegrape Network page about berry moths.
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: 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.
Links for further research:
Photos to illustrate planting method
See section entitled “Care of Bearded Iris”
Thorough explanation of planting, division and care. (One caution: The article recommends adding sand to help drainage, but sand should NOT be added to our North Texas clay. If you need to amend a new planting bed for better drainage, use expanded shale along with the compost.)
Placement of iris “toes” and “heels” impacts the long-term growth of the clumps
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.
The following links discuss bulb selection, soil preparation, planting, fertilization, wildlife deterrence and maintenance.
For help in deterring wildlife, refer to the video entitled “Planting Spring Bulbs,” which is embedded in the article
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:
- History of the Cora Van Wingerden family:
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: 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.
Native Plant Society of Texas article about Monterrey oak
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/blog/2018/09/03/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. For more information and control measures, visit this site.
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.
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.