Time Frame

Crape myrtle trees naturally lose their leaves over the winter months in U.S. Department of Agriculture hardiness zones 6 through 10. They endure a dormancy that helps reinvigorate them and time their growth for spring once warmth returns. The best time to conduct pruning is during this dormancy just prior to the appearance of new leaves. In the Deep South or California, trim in February. Farther north, trim from late February to March. In USDA zone 6, winter cold often kills back crape myrtles to the roots and they grow more like perennial shrubs. Cut dead stems back in late March.

What to Trim

Annual trimming in early spring tidies up the crape myrtle tree and improves its branching structure. First, remove any dry, dead branches and suckering shoots from the surface roots or trunk. Make cuts flush with the trunk with a hand pruners. Trim off dried seed clusters across the canopy, making the cut just above a dormant bud. There's no drastically need to reduce branch length -- only cut into branches less than the size of a pencil. Branches that rub against each other, grow toward a building or pose a safety hazard, such as encroaching on a walkway, should also be trimmed. Any branches 3/4 inch or larger in diameter are best severed with a loppers or pruning saw.

Trimming Benefits

Horticulturists with Virginia Cooperative Extension note that crape myrtles don't need annual pruning. When young, prune to train the tree to have a good trunk and branching structure. This allows the tree to attain its naturally size and form and produce strong branches and ample foliage to make food. This reduces the need for constant pruning once the tree ages. Crape myrtles produce their flowers on current year's growth. The more natural side branches in the canopy, the greater number of flower clusters in summer across the entire tree.

Avoid Bad Pruning Practices

Bad pruning techniques abound across the southeastern United States regarding crape myrtles. Colloquially called "hat-racking" or "crape-murder" by trained arborists and horticulturists, the worst practice seen is arbitrarily cutting back trees to a short height with large trunk wounds known as topping. Virginia Cooperative Extension mentions this shocks the crape myrtle tree by creating massive wounds to heal, leads to make weak-stemmed regrowth that susceptible to aphid infestation, and reduces the number of summertime flowers. If coppicing is done at an improper time or is too severe, crape myrtle trees die.