It’s prime time for these critical North Texas gardening activities. What to do now

Dec 23, 2023

Put a big red star on your garden calendar this weekend because it's prime time for several critical gardening activities. For the most part, they’re completely unrelated to one another, so my notes may seem a bit random. The common bond between them will be the critical nature of the timing.

Crape myrtle bark scale. This is a slow-moving insect pest that invaded the Metroplex in 2004. We didn't know where it came from. We just knew it was big and ugly — they looked like mealy bugs on steroids. The pest turned out to be a scale native to China that somehow sneaked past plant quarantines and into the United States. Now we have them clear across the south.

Many gardeners notice the white insects, but even more people observe the sticky honeydew they leave behind on crape myrtles’ leaves and stems and on hard surfaces beneath the plants. Still more homeowners complain of the black, sooty mold that grows in the honeydew substrate. As a journalist, I get very few questions about how to eliminate the scale insects, a few more about how to get rid of the sticky surfaces, and scores regarding the black mold.

What you can do: If you apply a systemic insecticide as a soil drench around the drip line of your crape myrtles now (mid-May), you can prevent the outbreak of crape myrtle bark scale insects this year. That will prevent the honeydew and therefore the mold.

The bonus is that you also will prevent crape myrtle aphids with the same treatment. This application must be made within the next week or two. Dormant oil applications in the winter do not work on this scale insect, and aphid treatments later in the summer will come too late because your plants will already be coated in honeydew.

Here's one final side note about how new insects rise and fall. Looking back to 2007, when we had the worst year ever for crape myrtle bark scale, there seemed to be no natural predators. Then, out of the blue, an unusual ladybug flew into town. It has black wings with two distinctive red dots, one on each wing, giving rise to the name of the "twice-stabbed" ladybug. They literally devoured the scale insects like tiny vacuum cleaners. They may be one reason that our populations have reached more of an equilibrium in recent years.

Nutsedge. No weed strikes fear in the hearts of gardeners any more than "nutgrass." Once it got a good start, we really didn't have a reliable means of getting rid of it short of removing the top foot of soil and replacing it entirely.

The main problem was that it produced the little "nuts" that resembled tiny coconuts. They gave rise to the common name of the plant that's more properly called "nutsedge." When we tried to pull it out of the ground, they would break loose and give rise to more weeds.

Nutsedge is not a true grass. Grasses all have round stems. Think about corn, bermudagrass, Johnsongrass and any of the ornamental grasses you might have in your yard. Those plants all have round stems. Now go out and roll the stem of nutsedge between your index finger and thumb and you’ll discover its triangular nature.

Why does that matter? Because regular grass-killing sprays such as the glyphosate products don't control it. But thank heavens for a new category of herbicide that came into the market 25 or 30 years ago. Image was originally introduced for control of nutsedge, and when I used it, I was very pleased with the results. It did exactly as I’d been told it would do. But it did so differently.

You apply Image as a heavy spray to affected areas. You can also use a sprinkling can as long as you’re careful to get uniform coverage. Follow the application with a deep watering because, unlike most herbicides, Image must enter the plant through its roots. It doesn't matter how much water you use to apply it. You just need to be sure you apply the amount in the bottle to the square-footage it says it will cover, then water it in thoroughly. If you do that the nutsedge will gradually disappear over the next several weeks.

Why is mid-May important in this? The manufacturer told me that for the Fort Worth/Dallas area we would need to make two applications for full control. Those two treatments would need to be 30 days apart and both would need to fall between May 15 and September 15. (Not that you’d want to wait, but that means that the latest date you can make your first application would be August 15.)

Image is cleared for use on most turfgrasses grown in Texas, but read and follow label directions. You’ll also see that it can be used around many types of ornamental plants. Be sure you get the original Image product intended for control of nutsedge. Under the Image brand, the manufacturer has since added other ingredients for other uses, and it should not be used as I have described. Again, check the instructions.

For the record, another product called Sedgehammer is also effective against nutsedge. It is used more by landscape contractors, but you may see it where you do your garden shopping. It's also quite good.

Finally, our catch-all bin. It's warm enough now to sow bermudagrass seed for starting new turf.

Soils have also warmed enough for planting hot-weather annuals including vinca, caladiums and ornamental sweet potatoes.

If you still have St. Augustine with yellowed blotchiness, that's all root rot. The fungicide Azoxystrobin should slow or stop it so that the lawn can get back to normal good summer growth.

If it's been eight weeks since last you fed your lawn apply an all-nitrogen lawn food that has 30% to 40% of that nitrogen in slow-release form. Do not apply nitrogen to St. Augustine after mid-June to lessen the chance of gray leaf spot during the summer.