By Sandra Tarpinan
One of Virginia’s most popular yet mistreated landscape plants is the beautiful crapemyrtle (Lagerstroemia indica, L. fauriei, and L. indica with L. fauriei or L. speciosa hybrids ). They are loved for their long summer bloom period and range of flower colors. Added to their beautiful flowers are interesting seed heads, lustrous green leaves that change to bright fall colors, and subtle-to-stunning multi-colored bark. It is a plant with true four-season interest and appeal.
Crapemyrtles are low-maintenance and easy to grow. All they need are sunny locations and soil with moderate moisture and fertility. They generally require a minimum amount of pruning when well-maintained and properly chosen to fit the space where they are planted. A misconception that crapemyrtles need to be severely cut back in late winter or early spring in order to flower well in summer has led to the unhealthy practice of “topping” these plants — cutting stems back at an arbitrarily chosen height.
Never Top a tree!
Even a Crapemyrtle
Topping crapemyrtles, a practice nicknamed “Crape Murder,” is harmful in many ways. It is regarded as an unacceptable practice by trained horticulturists and arborists. Research shows that stem decay significantly increases when topping cuts are made, and that more dead branches also occur within the canopy.
Topping crapemyrtles results in numerous fast-growing shoots originating from the “topping knuckle” that forms on the top of the cut stems. The natural shape and structural strength of the plant is ruined. Topping can greatly reduce the number of bloom days, because only one main flower cluster is borne on the end shoots instead of many smaller flower clusters with staggered bloom times. The new shoots are soft and poorly attached. They often break because they cannot support the single large bloom on the end of the shoot. The soft shoots are also more susceptible to pest problems (especially aphids). The damaged tree may also produce large numbers of ugly basal suckers.
The correct way to prune a crape myrtle involves enhancing its natural form. Crapemyrtles naturally grow as small upright or vase-shaped trees with multiple trunks. Because crapemyrtles are summer-blooming trees, producing flowers from new wood or current season stems, the proper time to prune is late winter or early spring prior to new growth. Removing dead, diseased, broken, crossing, and rubbing branches early in the tree’s life avoids the need for yearly pruning.
Starting at ground level, follow the trunks upward to where they begin to branch, focusing on the interior of the tree rather than the outer edges. To remove a branch, follow it back to where it joins a larger branch or trunk. Notice the swollen branch collar at the point where the two branches join. Using a pruning saw or loppers, remove the branch by cutting just above the branch collar, not quite flush with the trunk. If the branch was removed correctly, the branch collar left behind will extend out no more than half an inch from the trunk. Clean up the interior of the tree by cutting off small twiggy branches that grow from the main trunks. This is best done using hand pruners. You can also remove seed pods and trim off the ends of branches that are less than pencil-sized in diameter.
Crapemyrtles that have previously been topped can, to an extent, be “untopped.” Select two or three of the stronger shoots on each “topping knuckle” and prune the others off. Then prune back the selected shoots above outward facing buds to begin to develop a new branch pattern. The plant will never again have its true or natural crapemyrtle form, but it can be improved.
A helpful online resource is the Virginia Tech publication, “Pruning Crapemyrtles” (VCE 430-451) by Bonnie Appleton and colleagues, which details the damage caused by topping and describes correct pruning techniques at www.pubs.ext.vt.edu.
For techniques to prune back the height of a crapemyrtle that is interfering with power lines or other risks, see hort.ifas.ufl.edu.