Once crepe myrtles have bloomed and shed their flowers, they will set seed. The small round seedpods or capsules usually weigh the limbs down, making them sag. Using a sharp pair of clippers or hedge trimmers, cut off the seedpods. New shoots with buds will quickly appear, and you will get a second bloom.
Sometimes people are hesitant to remove seedpods because they think the round capsules are flowerbuds. This is not so. The seedpods are larger than the flowerbuds and extremely hard.
If temperatures stay warm into the fall and you continue to remove spent flowers, you may even get a third or fourth bloom out of your crepe myrtles.
"Crepe Myrtle Pruning Tips" is from the June 2002 issue of Southern Living.