Q: My recently purchased home has a number of 15 – 20 feet high crape myrtles. They appear to have been improperly trimmed since the limbs have round “knobs” with sucker-like shoots coming from them. Can I trim the limbs below the knobs?
A: My advice for fixing “knobbed” crape myrtles is to cut just below the knobs now and then wait until April for spring growth to begin. At that point you’ll get several sprouts from just below where you made your cut. Wait a few weeks to see which ones are most vigorous and most vertical. Clip off the ones that grow sideways but leave two vigorous, vertical sprouts growing up from each previously knobbed branch.
Allow the sprouts to grow 2 – 3 feet and then clip off the tips. This will make them resprout, probably at the height you want blooms to appear. Let them bloom next summer. When next December rolls around you can cut the long arching branches back to a diameter somewhere between thumb and pinky finger size.
This whole process should yield a multi-trunked, “V-shaped” crape myrtle that will require only pruning the limbs back to 1/2 to 3/4 inch diameter each winter.