You hear it every winter and early spring, “don’t murder your crepe myrtles,” but I cannot ever remember showing the results. Well this summer’s examples of heavy flower blooms bending the week shoots are everywhere. So, what should we do except know better next year? While nothing will correct the problem now, there are a few things that can take some of the stress off of stems that might break. Look up into the center of the plant, and if there are lots of small stems that are helping to pull down the long shoots, remove them (it is fine to do it now). If the blossoms are so large that they have a chance of breaking the stem, cut them just below the head of blossoms as soon as they start to fade. It will help the stems stand more erect and often times allow the stems to produce a second crop of smaller blossoms. And finally, when the plants finish blooming, select several good long branches on each stem that has been cut back over the years and remove all others. This will be the start of having beautiful specimens like the Natchez ones shown above. Remember, common crepe myrtles are small trees, but the good news is there are many selections with sizes that will grow the height you desire without butchering them every year.
More about pollarding crepe myrtles.