Crepe Myrtle

Since crape myrtles bloom on new wood late in the season, you can prune them now. However, we do not recommend that you top the plant. You can encourage blooming and improve the appearance of the tree by removing all of the lower limbs from the main trunks well up into the canopy of the plant. Also, remove any root suckers that are springing up around the base of the tree. You may find the following publication to be helpful;
https://pubs.ext.vt.edu/430/430-451/430-451.html