When and how do I prune crepe myrtles?

Published 7:20 pm Thursday, November 8, 2018

Crepe myrtles (Lagerstroemia indica) are one of the most-planted small trees in the South. They are very resilient trees that boast multi-season interest. They have lush green leaves through the spring and summer, beautiful blooms that last for more than a month in most cases, exfoliating bark that provides winter interest, and an arching umbrella shape when able to mature. These trees are used as focal points in landscaping, borders, city streets and even parking lots. Crepe myrtles are very resilient trees and, like a Timex, they take a licking and keep on ticking!

The perception among homeowners and landscapers alike is that you must severely cut these trees back to encourage more blooms and keep their size in check. This is called Crepe Murder! Unfortunately, this actually has quite the opposite effect. Trees are severely stressed when we cut them back in this manner, and often we are shortening their lifespan. Crepe myrtles, as with many tree species, will respond to this type of pruning with rapid growth the following growing season. The tree will put its energy into growing as many stems/branches as it can and then reproduction (flowering). These new stems will be weakly attached and subject to breaking in a strong wind.

While severe pruning will affect flowers, it will not be in the manner in which we are hoping. Flowers will be larger but will be singly born on the new stems as opposed multiple flowers on one stem. The bloom period on the severely pruned crepe myrtles will be delayed and will not last as long because there is only one flower per stem. Since the new stems are weakly attached they may not support the weight of the larger flowers causing them to break. There is one other effect of pruning in this manner that could actually kill the trees, especially on larger branches, this can cause them to split and rot if we have a cold winter as we did last year. I have seen dead crepe myrtles across all of my four-county work area. Most of them a result of sever pruning last winter.

Okay, enough Murder She Wrote! So, when and how do you properly prune crepe myrtles? Late winter between February and March is the best time to prune most woody shrubs (unless they are late winter or early spring bloomers, prune these after blooms are spent). The proper way to prune is to first exercise the three D’s to take out dead, damaged or diseased wood. After this is done, look for branches that are crossing over one another or rubbing together as well as any inward growth (growing towards the center of the tree). The goal of pruning ornamentals is to open the tree up to allow for air movement and to remove your 3-D (dead, diseased or damaged) wood. In the summer, after blooms have faded, you can dead-head (no, this is not akin to Jerry Garcia) the flowers to encourage rebloom, extending the bloom period. This is done by snipping the branch just below the spent flowers. On mature trees, this is not feasible, but on the dwarfing cultivars, this is a standard practice.

There are nearly 100 cultivars listed in the “Manual of Woody Landscape Plants” (6th Edition, Michael Dirr). Cultivars range in size from two feet to more than 40 feet tall and wide with pink, purple, red and white flowers. The best advice I can give in selecting a cultivar for planting is to do your research and find the right plant for your space!

If you are having an issue in your home garden or landscape, send your questions to Gene Fox, Consumer Horticulture Agent with the North Carolina Cooperative Extension Service, please email at Gene at gene_fox@ncsu.edu. Learn more on Facebook at the Blacklands Area Horticulture page or visit the Extension Office located at 155 Airport Road in Washington!

Gene Fox is a consumer horticulture agent with the North Carolina Cooperative Extension Service, covering Beaufort, Hyde, Tyrrell and Washington counties.