Question: I purchased and planted two “Dynamite Red” crepe myrtles in the spring, and they did well this growing season. Although they are supposed to withstand the cold weather in our region, I do not want to chance it and leave them unprotected from the winter winds. Can you recommend a method of protecting these trees for the winter months?
Answer: There are about fifty species of crepe myrtle (Lagerstroemia), some evergreen and some deciduous. Here in Western Pennsylvania, there are only a handful of crepe myrtles that are said to survive the winter. Most varieties of this quintessentially “southern” plant are hardy only to USDA zone 7 and above. The selection you have, L. indica “Dynamite,” was bred to be hardy to zone 6, though in rough winters it will die all the way back to the ground and may fail to bloom as a result. The ruffled, red flowers of this variety are real show-stoppers in mid-summer, and the burgundy foliage in the fall is an added feature.
To ensure crepe myrtle survives the winter in Western Pennsylvania, locate it in a sheltered spot; perhaps between two buildings or in a corner where it's protected from strong winter winds. Proper drainage is essential to winter survival as crepe myrtles resent water-logged soil around their roots.
To properly protect your crepe myrtle, wrap the plant with a layer of insulation. This can be accomplished by creating an open-topped, cylindrical wire cage around the plant using chicken wire or box wire fencing. Be sure the cage is a foot or two larger than the shrub is in diameter. The cage should also be about a foot higher than the top of the plant. If your shrub is very tall, you may want to prune the plant back by half of its height to make the cage a more manageable size. Once the cage is over the plant, use landscape pins to secure it to the soil, then fill the cage with straw or shredded leaves until the entire shrub is covered and well-insulated.
Because crepe myrtles bloom on new wood, you'll need to do any pruning in fall, winter, or very early spring. I find the perfect time to prune my own crepe myrtle is in the spring, just after I remove the cage and straw in early April. Doing so allows the plant to have enough time to develop new growth and flower buds by mid-summer.
Another shrub this technique works quite well on are mop-head hydrangeas (Hydrangea macrophylla). With this shrub, the buds form on old wood. It's essential to protect the stems through the winter as they house next year's developing flowers. The most common reason hydrangeas fail to bloom is because the unprotected buds do not survive the winter and freeze out. Insulating them with a wire cage filled with straw is very effective.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” and “Good Bug, Bad Bug.” Her website is www.jessicawalliser.com.
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