Even mild winters can damage plants

We usually think that winter damage in plants shows up after a harsh season of extremely cold temperatures, ice storms or prolonged snow cover. This winter damage is exhibited by dieback of twigs, sunscald, browning and even loss of leaves on broadleaf evergreens such as boxwood and nandina.

Yet winter damage in plants sometimes shows up several weeks after winters that seem extremely mild. This year is a case in point.

Over the last month I have looked at several crape myrtles that have suffered from winter damage. All of the above-ground branches were killed this winter. New shoots are now slowly coming back from the base of the shrub or from the root system. This is not an uncommon occurrence in our area.

Crape myrtles are commonly found in the southeastern United States. The milder winters and the hot, humid summers are just the right conditions for their rapid growth rate and vigor. Normally they do well in the region during our summers, but sometimes have to struggle to tolerate our winters.

I wouldn't say that we had a harsh winter this year. I can remember very few days in the teens. We did have one heavy snow, but it was gone within a week. Nothing seemed to be causing any stress on plants.

What we did have was warm late winter days, followed by some extremely cold temperatures for late spring. The warm late winter days sent a signal to the crape myrtle -- spring is right around the corner so you can start doing your spring thing.

Physiological changes began to occur within the plant. These changes resulted in the loss of cold hardiness. Then when the late spring cold spells hit, a lot of tissue was frozen because it was no longer internally protected from cold temperatures. The frozen tissue died, and the symptoms of twig dieback, leaf burn and leaf loss resulted.

If your crape myrtles are seemingly dead, do not give up hope yet. I have seen crape myrtles that are "dead" come back from the root system as late as June or July. You just have to wait for a while. Don't make a decision on whether or not your crape myrtle is dead until at least the first of June. If it doesn't come back by then, go ahead and rogue it.

If your winter-damaged crape myrtle has started to come back from the lower part of the stem or from the roots, prune out any dead branches on the shrub. Leave the new tender shoots. They will be the foundation for your new shrub.

Make sure that you fertilize your damaged crape myrtle this spring. It might need some extra nutritional help to get back on its feet. Use a fertilizer similar to 19-8-10 with micronutrients.

In addition when we get our normal hot dry period during the summer, make sure that you water your crape myrtle thoroughly every two or three weeks. You want to minimize any additional stress caused by drought.

During this spring I have also seen a lot of winter damage on boxwood, nandina and roses. You can follow a similar recovery program for these plants just as I described for crape myrtle.

Send your gardening and landscape questions to Paul Schnare at P.O. Box 699; Cape Girardeau, Mo. 63702-0699 or by e-mail to news@semissourian.com.