I believe it is in the spring if you have to do it at all. Pruning is not required for blooming, but apparently some people think so.

Be careful not to overprune (a practice often called "crepe murder"), just a gentle shaping should be all that is required. Excessive pruning, especially whacking off of limbs that are more than an 1/2 inch thick will force too much new growth and create ugly "knuckles" that you have to look at in the winter.

Perhaps you already know all this, but I thought I'd mention it.

Here is a link that might be useful: UGA article on proper pruning

I sometimes think that many people get their crepes whacked because everyone else in the neighborhood does it. Just keeping up with the Joneses & not wanting to be different.

I know for a FACT that many people think that they are supposed to chop them back, and that they won't bloom unless you do. I also know that landscaping companies use the task as a way to keep busy during the slower winter months.

The truth is, blakeas, once you've chopped the tops of your crape myrtles, you've destroyed any chance at winter beauty. They do not need to be pruned in order to bloom, and don't even need their seed heads clipped off. Simple shaping is all that is helpful, and this is best done in the dead of winter or early spring before new growth. That's when you can best see what you are doing.

Also remember that everywhere you cut, you'll get a bunch of branches (4 or 5) sprouting out of that cut. So it's a useful way to decide which branches to cut off - if you want more fullness in that spot, cut it off. If you don't, leave it.

Good point, sandman. But if a person makes a 'proper' cut, that kind of suckering won't happen. A proper cut is when you make a cut AT an outward growing branch, rather than simply stump cutting. (Called pruning to a lateral branch.)

Here is a link that might be useful: {{gwi:839731}}