Published in the Contra Costa Times on
Q. How and when should I prune my crape myrtle?
A. Crape myrtles (Lagerstroemia indica) are very popular landscape plants. They bloom prolifically in the hot summer months, have brilliant fall foliage and striking gray to cream winter bark.
There appears to be some confusion about the correct way to prune crape myrtles. It has become common practice to behead them, lopping off all the top branches. There is mistaken belief that this is necessary to promote flowering. In some areas this is called crape murder.
Flowers occur on the new growth produced in the spring, so light pruning in late winter encourages the production of flowering branches. If the trees are tipped back lightly right after the first flush of bloom, some cultivars are likely to bloom a second time. Cutting the trees back heavily can shock them and slow down the growth of flowering branches. If you don’t prune at all, the flower clusters that emerge in the summer will be smaller but more prolific.
If the trees are being pruned back severely to keep them small, consider replacing the one you have with a semi-dwarf cultivar. There are lots of new semi-dwarf cultivars available that will have a final height of 7-15’. A few of the smaller named cultivars are ‘Tonto’ (red flowers), ‘Acoma’ (white), ‘Comanchee’ ( light pink) ‘Zuni’ ( Lavender)—all resistant to powdery mildew when planted in full sun. Crape myrtles must have full sun to bloom well.
When you prune the plants in winter, remove crossing and damaged branches, and shoots that are headed into the middle of the tree. Be sure to cut just outside the branch collar, that swollen area just past the point where the branch attaches to a trunk. Don’t coat the cuts with anything. The branches on the outside of the tree’s canopy should be cut back only if needed, and no more than one-third of the length.