Want beautiful crape myrtles for the rest of the year? Here’s what you must do in May

This time in May is critical to the success of your crape myrtles for the next nine months. That includes how well they grow, bloom and look in your landscape. Let’s cover the details.

Were they hurt by the cold?

Some varieties of crape myrtles were hurt by the extreme cold of February 2021. Some were damaged by the ice and cold of winter 2022. As those plants have leafed out this spring, they’ve been the ones with sparse foliage at the tops of their branches. Thin canopies have left you wondering if the plants are sick or dying. Odds are they’re just suffering cold damage and need to be cut back to the ground so they can regrow.

Let’s go over that again. If you have a crape myrtle trunk that was hurt badly by cold, you can usually get a great looking plant restored far faster simply by cutting it back to the ground and allowing the new shoots that are probably already sprouting up to develop as its new trunks. I saw hundreds of examples of exactly that last year alone. Tree-form crape myrtles that had been 15 or 20 feet tall were almost killed by the cold. Landscapers cut them back to within 2 inches of the soil line, and by first frost last fall they had already regrown to 10 or 12 feet. When you do that you just have to select the 3-5 stems you want to retain as the new trunks for your crape myrtle tree.

Just to have put it into the record, varieties that are more commonly hurt by winter cold here in North Texas include Natchez, Sioux, Tuscarora, Muskogee and Country Red as well as most of the miniature, weeping varieties with the South Louisiana and Cajun names (New Orleans, Lafayette, Baton Rouge, Cordon Bleu, etc.).

Do they have blackened bark?

Plants with black trunks have a fungus called sooty mold, but before you hit the panic button, let me ease your anxiety by telling you that it’s essentially harmless. It lives on the honeydew excretions of crape myrtle aphids and crape myrtle bark scale. It gets none of its nourishment from the trunks or branches of your crape myrtles. In fact, the mold will be cast off with the sloughing bark as the trunks and branches grow larger this spring and summer.

If you’re really concerned about the sooty mold you can use soft sponges and a bucket of warm, soapy water to scrub the mold off the trunks. That’s up to you, but as mentioned, most of it will be shed with the bark.

The bigger issue comes with the two insects. You really don’t want them on your plants, mainly because they make such a mess. The honeydew is sticky, almost like tacky varnish, and very glossy. It catches debris and makes the plants look unsightly.

To prevent bark scale, aphids and therefore the sooty mold, apply a soil drench of Imidaclopid systemic insecticide around the drip line of each plant in mid-May. That means now! Let it soak into the root zone so it can be taken up through the plant where it will be lying in wait for any of the sucking insects. That list includes aphids and bark scale. This recommendation comes after extensive research by Texas A&M entomologists and horticulturists, and it works very well.

How do you get maximum blooms?

You start with a good planting location. They need full sun, ample space to grow without repetitive shearing to keep them in bounds, and a ready supply of moisture.

Crape myrtles produce their flower buds on new growth. The sooner you can promote vigorous new growth in the spring, the more quickly your plants will come into flower.

Nitrogen promotes new growth. That’s why you want to use a high-nitrogen, perhaps even an all-nitrogen fertilizer on your crape myrtles to get the most rounds of flowers. And the nitrogen must be applied with a thorough watering. New growth won’t happen with dry plants.

You never want to top your crape myrtles. Topping sets back their new growth. Take note this summer of plants (of the same variety) that were topped and others that were not. The plants that weren’t pruned will bloom 4 to 6 weeks earlier and they’ll bloom one or two more times over the course of the summer. You really don’t even need to remove the old flower heads as they drop their petals. New growth and new flower heads will develop around them.

Best time to plant crape myrtles will soon be here

By late May and early June nurseries will be filling their aisles with crape myrtles in bud and bloom. Those of us who work with them on a daily basis estimate that there are about 150 named varieties in the nursery marketplace. Of those, probably only 40 or 50 could be described as commonly sold. In many cases they’re proprietary varieties introduced by large wholesale growers with a great deal of promotion. In other cases they’re types that grow rapidly and that can be made ready for sale faster than comparable types of the same colors. (That’s not always the best criterion.)

Here is a list that we on the Crape Myrtle Trails of McKinney board have prepared. These are types we feel are best-suited to our area. https://crapemyrtletrails.org/varieties/best-crape-myrtles-by-size/

You can hear Neil Sperry on KLIF 570AM on Saturday afternoons 1-3 p.m. and on WBAP 820AM Sunday mornings 8-10 a.m. Join him at www.neilsperry.com and follow him on Facebook.