Q&A – Ask Neil: July 31, 2025
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Important favor: I’ve been covered up so far this year with questions about live oaks losing chunks of bark. Rather than continuing to answer the same questions weekly, I’d ask that you look back to previous issues. You’ll find several replies that I’ve posted. Thanks!
QUESTION 1
CAN I STEP BACK ON TREATMENTS FOR TARR NOW?
Question: I have been treating for take all root rot (TARR) on my St. Augustine this year with Scott’s DiseaseEX as directed on the label every 4 weeks. It seems to be under control now. Can I go to a 6-week interval? Randy L., Dallas.
Answer: Yes. I wouldn’t expect TARR to be a problem at current very high temperatures. It might resume in the fall, however, so keep your eyes open.
It’s worth noting that the active ingredient Azoxystrobin does also slow gray leaf spot (a hot-weather leaf disease) and brown patch fungus (a fall leaf blade disease), so be on the lookout. You may need to resume your treatments, but for a different fungus.
QUESTION 2
WHAT ARE YOUR FAVORITE PURPLE, DARK PINK, AND WHITE CRAPE MYRTLES?
Question: We are replacing a 75-year-old Shumard red oak and are considering planting a crape myrtle. What are your favorite purple, dark pink, and white types that might double as a shade tree? Jon M., Dallas.
Answer: Twilight is an outstanding tall dark purple. My favorite is Catawba, but it’s a bit shorter, to 16-18 ft. tall. It’s a lighter purple that blends beautifully with all crape myrtle colors, also with any brick and roof color. Choctaw would be my personal choice for pink. As for the white, I’d plant Glendora White or Sarah’s Favorite White. I have Glendora along our driveway and it has survived all cold in North Central Texas (McKinney, just a little bit colder than where you are). Natchez has frozen to the ground several times, for us, as has the lovely popular dark pink Tuscarora and very tall lavender Muskogee.
One editorial thought: Unless you have a zero-lot-line home, coming down from a red oak to one single crape myrtle may end up leaving you with a very small-looking shade tree. If you’re just trying to downsize, consider a Little Gem southern magnolia.
QUESTION 3
HOW CAN WE KILL CRAPE MYRTLE ROOT SPROUTS?
Question: We removed a crape myrtle that was no longer welcome in our new home’s landscape. New shoots now continue to poke through the new landscape. What will kill them? Andy E., Bedford.
Answer: A broadleafed weedkiller (containing 2,4-D) applied carefully to each new shoot when it’s 5-6 in. tall will kill it back to the main root from where it originated. These are all tethered to large roots, and they will continue to sprout out for a year or two. If you can dig and remove the mother root in each case, that will get rid of the source. Otherwise, treating with the herbicide will discourage them.
QUESTION 4
WHAT CAN I DO TO HELP MY NEW FELIX MAGNOLIA?
Question: I planted a fair-sized Felix magnolia this spring. I amended the soil to raise the acid, but the leaves are turning brown regularly. However, new leaves are coming out. What can I do? Marilyn Z., Frisco.
Answer: Felix Jury magnolia was hybridized in New Zealand. It’s a stunning selection of deciduous magnolia (unlike our native evergreen southern magnolias) that was chosen for its very large deep pink blooms.
Its needs are going to be similar to the hybrid saucer magnolias you see more often in the Texas nursery trade. I’ll list the ideal growing conditions.
• Hardy to Zones 5-9, but prefers the cooler areas with summer highs in the 80s, certainly not approaching 100.
• Acidic soils 5.5-6.5. I live in Collin County as you do, and our soils are in the range of 7.5. That would require almost a total replacement of the soil with a mixture of sphagnum peat moss and well-rotted compost or finely ground pine bark mulch in equal amounts (no black clay soil). Further, Metroplex irrigation waters have even higher pH levels, further compounding issues with availability of iron. But that won’t show up for a couple of years or longer.
• Morning sun until mid-morning, then protection from the hot afternoon sun. Especially, do not plant them against reflective surfaces.
• Water deeply every two days. Soak your tree with an amount equal to the soil ball from the container in which it was growing. Use a garden hose with a water bubbler or water breaker to hasten the watering. If you miss one watering your plant will lose roots and damage will be done for the rest of the growing season.
• In fairness to you, this will not be an easy plant to grow in the soils of Frisco. Hopefully the nursery warned you of that fact. That’s why you don’t see them being used any more often than you do. Good luck with yours! I hope it performs well. If you decide you need to move it, do so in winter while it is dormant.
QUESTION 5
WHAT IS KILLING MY PURSLANE?
Question: What is killing my purslane? Within the past few weeks my purslane beds have started dying. I see small white spots (fungus?) dotting the stems, also on the mulch, decorative rock, and brick on my house. Help! John M., Frisco.
Answer: Honestly, I have no idea. I have grown purslane since 1971 and I have never seen it being eaten by anything, but those bare stems do look like caterpillars, grasshoppers or something chewed their way through it. The white masses could be droppings, perhaps even of birds. But I don’t see anything actively working in the photos, and it’s odd that you see it on the vertical “walls” of the decorative boulders, not on the top surfaces. The purslane is toast, so I’d suggest reworking the beds and planting something for fall color over the next couple of weeks. I can’t see the white specks well enough to tell what they might be, but you could take a toothpick and flick a couple of them off. Most of them look like they have already fallen loose. If so, perhaps you could use the hose and a pressure nozzle to clean things up a couple of days before you do the bed prep. I suspect this is just a one-time thing.
QUESTION 6
SPIDER MITES HAVE BEEN TERRIBLE. WHAT CAN WE DO?
Question: Spider mites have been worse this year than any year I can remember. Tomatoes, squash, cucumbers, morning glory plants, moonflower vines, and others. Sevin spray has not helped. What can I do? Debby K., Keller.
Answer: Spider mites have 8-legs, meaning that they are more closely related to ticks and spiders than they are to insects. We no longer have a specific miticide for home gardener use since Kelthane left the market 15-20 years ago. About all we can do is use a general-purpose organic or inorganic insecticide that does include spider mites on its label. Your Texas Certified Nursery Professional will be able to show you several. Whichever one you select, it won’t give total control, but it will help.
Regarding Sevin (Carbaryl), you will notice that it is specifically not recommended for use on spider mites. Not only does it not kill them very efficiently on its own, it also kills their natural predators.
QUESTION 7
WHY DON’T THE FLOWERS ON MY HIBISCUS OPEN?
Question: This is a first-year hibiscus. It appears to be healthy. It is watered and fertilized frequently, but its flowers do not open. I see no signs of insects. Just no flower buds opening. What gives? Paul T., Temple.
Answer: On first sight I would guess that your plant is root-bound. It’s probably getting too dry each day, even if you’re watering it often. Hibiscus plants need to be kept growing vigorously by fertilizing with a high-N water-soluble plant food and soaking the plant daily, perhaps even twice daily when it’s quite warm. You might try repotting it into the next larger pot size sometime soon. I cropped your photo after I wrote my reply, and I also wonder if it might help the plant if you were to move it to a spot with just 1-2 hours less hot, direct afternoon sun. Whatever is causing the many buds to abort just before opening, the problem is marginal. It won’t take much to correct it once we get it figured out.