Q: I have a very old post oak that is declining. Where can I send a sample to be tested for disease?
A: 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.
Q: 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?
A: 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
Q. Moles are tearing up my yard! What can I do?
A. 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
Q: The guy who cuts my grass told me to run each irrigation station 10 minutes three times a week, but my grass looks pitiful.
A: 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.
Q: 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?
A: 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.
Q: How can I get grass to grow under my trees?
A: 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.
Q: When should I apply pre-emergent herbicides to my lawn?
A: 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.
Q: I just moved to a new house. I have no idea how to take care of the lawn.
A: 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.
Q: My St. Augustine grass is looking really bad.
A: 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.
Q: Feral hogs rooted up my lawn and left a huge muddy mess. Can I overseed now with rye (November)?
A: 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.
Q: When should I plant broccoli, cabbage, and other winter vegetables?
A: 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.
Q: My tomato plant has spots on the leaves. What is wrong with it? Do I need to spray it?
A: 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.
Q. Why are tomatoes so fussy in our area? What varieties will do well here?
A. 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.
Q: 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?
A: 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).
Q: I’m a new gardener and would like to start a vegetable garden this year. Where do I start?
A: 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/
Q: Can I save vegetable seeds for next year?
A: 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.
Q: Will my spring tomatoes produce more fruit in the fall?
A: 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.
Q: Can I locate my vegetable garden over the septic leach field?
A: 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.”
Q: What is wrong with my grapes?
A. 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.
Q: What kind of black-eyed peas do well in Denton County?
A: Blackeye #5, Colossus, Mississippi Silver, Pink Eye purple hull, Texas Pinkeye, or Zipper Cream. For other vegetable/fruit recommendations, see the Vegetable Variety Selector.
Q: What variety of peach and pecan trees do well here?
A: 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.
Q: My plants look fried. I’m not at all sure I’m watering enough for this heat. Can you give me some guidance?
A: 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.
Q: When should I fertilize my roses?
A: 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.)
More information about what fertilizer to use depending on the type of rose is available from American Rose Society, “Fertilizers: When and How”.
Q: My roses have black spot. Is there anything I can do?
A: 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.
Q: Some of my trees are already dropping leaves. Why is this happening? Should I be worried?
A: 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/
Q: What is making these holes in a tree? Could it be borers?
A: 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
Q: One of my favorite old trees has ice damage. Can it be saved?
A: 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”.
Q: My tree has what looks like a large mushroom about midway up the trunk. Should I cut it off?
A: 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 International Society of Arboriculture Arborist Search page. You can input your zip code to find an arborist in your area.
Q: Can you tell me how to plant a tree properly?
A: 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
Q: When should I prune my peach tree?
A: 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
Q: When can I transplant a tree?
A: 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.
Q: Twigs are falling off my pecan tree. What is causing this?
A: 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.
Q: What walnut varieties are recommended for North Texas?
A: Thomas or Carpathian.
Q: My well water is salty, and I am having trouble growing plants. What can I do?
A: 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.
Q: My yuccas are being destroyed by tiny bugs with a red head. What are they?
A: 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.
Q: There is black stuff on my trees and many of my plants. It looks like mold.
A: 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 back side of leaves. To the naked eye, they usually appear as tiny white dots.
Q: There is something that looks like vomit on my begonias.
A. 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.
Q: (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?
A: 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.