Every year at this time of the season, I cringe at the sight of the “bad haircuts” on what should be large, beautiful Crepe Myrtle shrubs. Homeowners, and even “professional’ landscapers whack back the stems on Crepe Myrtles at the same point they were pruned last year, and the year before that, and the year before that. What’s left is an ugly, twisted clump of stem at the tops of the shrub. This picture on the left is really bad. It’s even worse because it was a bad pruning cut, looking like it was just ripped off with a weed-eater or something, rather than a clean, sharp cut.
We call this practice of pruning Crepe Myrtles every year in the same place, just to give one something to do, as Crepe Murder. It does not actually kill the shrub, but it it does take away from the natural growth, health, and beauty of the shrub. These shrubs can grow quite large, with colorful displays of flowers all summer, especially in the more southern states. Oklahoma is on the northern fringe of climates where Crape Myrtles will thrive. With the warmer winters we are having, I can’t remember one where they were damaged by a hard freeze, which can happen. In that case, then yes, some pruning may be needed.
Otherwise, we recommend just to let them grow with minor pruning just to keep a nice shape and prevent from becoming too dense. If space allows, let them grow to 8, 10, even 12 feet or more. And if pruning is needed, don’t take out every stem at one time, but selectively prune for shaping.
For a good video on Crepe Murder, and how to properly prune these shrubs, visit here. And if you really want to do something at this time of year to help your Crepe Myrtle, apply a systemic insecticide and dormant oil. This will help prevent aphids and scale later on in the season, which are two pests which can harm Crepe Myrtles.