Q: I’ve heard you say to prune crape myrtles back to where the wood is about the width of a pencil or your little finger. My follow up question is this: WHY is it necessary to prune crepemyrtles? What would happen if I don’t prune them?
A: There is no reason at all to prune a crapemyrtle except to make it conform to your need for size and shape. They will flower whether pruned or un-pruned.
To clean up my plants, I like to remove dried seed clusters and all of the small twigs along the trunk every winter. I also cut out any root suckers around the base of my crapes. In a spot where the arching branches get too wide, pruning back to a limb diameter of one-fourth to one-half inch will maintain the vase shape of a tree form crape myrtle. I dislike intensely the wholesale, murderous “whack back” that ill trained maintenance crews perform. The resulting mass of foliage makes powdery mildew and aphid problems almost a certainty.