Q&A – Ask Neil: September 21, 2023
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WHAT IS KILLING MY PLUMBAGO PLANTS?
Question: I have four plumbago plants. One is a transplant from 3 years ago, one from 2 years ago and two from this spring. They are surrounded by rock with a hole in weed cloth. They get plenty of water, fertilizer, and I added a small amount of Ironite. What is killing them? Handa M., Austin.
Answer: A photo might have helped because I can’t tell if there could have been issues with the heat and drought (the two most likely causes), or if an insect or animal might have been feeding on them. Plumbago plants aren’t fond of our extremely hot weather and low humidities. The weed-blocking fabric might have been concealing some really dry soil.
CAN I PLANT A NEW SHUMARD RED OAK WHERE AN OLD TEXAS RED OAK DIED OF A ROOT FUNGUS?
Question: I had to take out a 75-year-old Texas red oak due to a root fungus. Can I plant a new Shumard red oak very close to the ground-up stump, or must the new tree be planted some distance away? Or should I go with a different variety of tree? Jon M., Dallas.
Answer: If you have a sure verification that a soil-borne disease was involved I would switch to some type of tree other than an oak. Chinese pistachio, cedar elm, pecan, or southern magnolia would all be large shade trees that would not share susceptibilities with the oaks. However, there aren’t a lot of soil-borne oak diseases that hang around to infect later plantings. Hopefully you had a certified arborist such as our advertisers (Arborilogical Services) in e-gardens on site for the removal. I do know that Russell Peters, one of their top people, has his Masters degree in Plant Pathology specializing in oak diseases.
WHEN IS THE BEST TIME TO TILL AND RELEVEL MY YARD?
Question: My bermuda backyard lawn is doing well, but it really needs to be leveled. I’ve made several attempts, but it’s futile. If I were to have the yard tilled and leveled, when would be the best time? Pam H., Sadler, Grayson County.
Answer: May or early June. I would begin by spot-treating any really troublesome weeds (namely dallisgrass) with a glyphosate-only herbicide. It will not contaminate the soil, so you can rototill it and start planting as soon as it’s had time to kill out the weeds (a couple of weeks).
If you intend to try to save as much of your sod as possible, your next step would be to rent a sod cutter and strip up the good grass and set it aside.
If you do not expect to save the current grass, you can spray the entire lawn with the glyphosate-only herbicide and wait the two weeks.
Next, rototill to a depth of 4-5 inches. Rake the soil to a smooth grade that drains away from your home. Finish by replanting the sod or by planting new sod or seeding new grass.
By waiting until late May or early June, the soil will be warm enough for the grass to take root and start growing quickly. Water daily unless it rains. Mow it as soon as it’s tall enough to justify it. Allowing new grass to grow beyond that will quickly weaken it.
If all of this sounds daunting, landscape contractors are used to doing it and either have, or are used to renting, the proper equipment.
(Great to hear from you, Pam.)
WHAT IS WRONG WITH MY ROSES, AND WHAT SHOULD I DO?
Question: My roses survived the drought, but now the leaves are turning different colors. Is this a result of drought? What can I do? Paula L., Carrollton.
Answer: To some degree this looks like the common rose fungal disease called black spot. For that you would apply a labeled fungicide. However, do a bit of Web searching first to see if that is indeed the cause. Rose rosette virus is so rampant across North Texas that I worry that it might be involved. Please see the detailed RRV information I keep archived on my website. Hopefully it will not be involved, but if it is, please read what I’ve written very carefully.
WHAT IS HAPPENING TO MY MARY NELL HOLLY?
Question: My 10-year-old Mary Nell holly is dying one section at a time. It’s in the shade and has had very little shearing over that time. It’s mulched, and I’ve watered it two times per week. What is going on? Donald P., Denton.
Answer: I’ll speak from my own first-hand experience of 46 years, plus hundreds of observations over the past half-century of helping Texas gardeners. I have seen two things cause this kind of die-out on larger hollies (Mary Nell, Nellie R. Stevens, Oakland, yaupon, etc.). On three occasions I’ve had woodpeckers attack specific tree-form hollies on our property. It was where the trunks were exposed and they riddled them until parts or all of the trees died. In each case the bases resprouted and grew in shrub-form.
In all the other occasions that I’ve observed on my own property and all across Texas, plants have gotten too dry one or more times. It can happen when one side of a plant’s root system gets enough water and the other side does not. That is usually because a sprinkler system isn’t delivering water uniformly. I can show you dozens of examples similar to yours in Dallas and Collin Counties where I live and travel.
I would be amazed if this were due to insects or any disease, and it’s certainly not due to a nutritional shortage. Hollies thrive in the shade unless it is extremely dense. This doesn’t look like that’s the case.
I think it boils down to the watering. “Twice a week” doesn’t specify how much or how long. At the extreme temperatures Texas encountered this summer what we thought was normal for watering would have been inadequate by 2023 needs.
HOW CAN I PLANT WILD SUNFLOWERS AND WHERE CAN I GET SEEDS?
Question: I’d like to plant wildflowers, especially the wild sunflowers I see along the highway. When should I plant them and how? Where can I find the seeds? Olga G-O, Dallas.
Answer: You’re talking about Helianthus annuus, also known as “common” sunflower. I like it, too, although I will warn you that it’s a rank grower. It will take over its space if you’re talking about planting it within the city limits.
But let me on move past that. You could collect seeds this fall off plants in vacant areas. If you get there before the birds, there should be thousands of seeds available in the heads. If a head is fully matured and completely dry you can cut it from the stem and drop it into a paper sack. When you get it back home, carefully open it up over a sheet of newspaper and save the individual seeds. Store them cool and dry in a zipping sandwich bag in the fridge over the winter.
I also found many sources of wild, or common, sunflower seeds online simply by searching “buy Helianthus annuus seeds.”
Plant sunflower seeds into a bare space (no turfgrass) next March after danger of frost has passed. You could also start some of them in 4-inch nursery pots for transplanting into your garden.
Consider, too, the possibility of growing Maximilian sunflowers (Helianthus maximiliani). They’re perennials (come back from their roots year after year). They bloom each fall about now, and given good moisture they can be handsome tall, upright flowers in the back of a mannerly perennial garden. They, too, are available online and occasionally in local independent retail nurseries.
WHAT IS WRONG WITH MY LAWN?
Question: My local nursery thought this was TARR. I applied iron, a fungicide, and fertilizer per their advice, but it didn’t get any better. I’ve checked for chinch bugs, but I don’t find any. I’m also unsure if I’ve been applying the right amount of water during the heat and drought. We also have lots of rabbits. I’m not sure if they affect lawns. Help! Jacob M., Plano.
Answer: I read your notes, then I chose the photos I wanted to include. Somehow, I had missed the comment about rabbits. I had zoomed in on the one photo to show all their pellets thinking I would surprise you. Silly me.
It’s certainly possible that TARR has also been involved in damaging your lawn, but I’m guessing the rabbits are the main culprits.
If you Google the simple question, “How do rabbits damage home lawns?” you will get dozens of matches, and almost all of them will refer to the soluble salts left behind by rabbit urine.
Water often to dissolve and leach out the salts. Do anything you can to shoo the rabbits on down the road into a native habitat. You might consider having the soil tested by the Texas A&M Soil Testing Laboratory over the winter to monitor levels of accumulated mineral salts. Send your sample in sooner rather than later to avoid the spring rush. You could actually do so now. Sampling and mailing instructions are available here.
HOW CAN I STOP TERMITES FROM ATTACKING MY OKRA PLANTS?
Question: How can I stop termites from attacking my okra plants in my vegetable garden? Dinba, Plano.
Answer: Dinba called one of my DFW-area radio programs last Saturday with this question. I told her I’d do some online research for an answer. Well, that yielded a big zero. (Okra being almost totally a southern crop, national websites and national researchers don’t give it any lip service or web space.)
So, I did what I should have done in the first place. I reached out to TAMU Extension Professor Emeritus Dr. Jerry Parsons, himself a vegetable specialist who speaks this language fluently. I also asked if there was any chance she might have been seeing fire ants at work. Here’s what he wrote back:
“Ants and especially fire ants love okra blooms and the aphids that congregate on the tender pieces of the stem and flower. Fire ants can literally destroy the pod-producing capacity of okra.
Termites are a different story. The termite referred to as terrestrial or subterranean termites get their nutrition from wood and other material containing cellulose. Paper, cotton, burlap, or other plant products often are actively consumed by termites.
Sometimes termites will even tunnel into the dead heartwood or pith of living plants. Most species of subterranean termites cannot digest cellulose directly and depend on single-celled protozoans and bacteria living in their hindguts to help digest the cellulose. Digested cellulose is then shared with the developing larvae, other workers, soldiers and reproductives. Termites can damage the trunks of trees as well as okra.”
You have a couple of things going for you with okra. You’re about to remove all the plants, so you’ll be able to rake and remove all the stem and root stubble. That will get rid of much of the overwintering stage of the insects.
Plant next year’s okra in a different full-sun part of your garden. Termites are native in our soil, so they may appear there, too, but crop rotation is always good practice.
You could apply a general-purpose insecticide to the entire garden space once it has been emptied this fall. That would give it at least three months, and for the okra planting area more like six months to get out of the soil. I wrote Jerry back to ask what he would recommend and he said you should try something with Spinosad to drench the fire ant mounds. He added that any product labeled for termites should work.