Ferguson: Tips on the persistent topic of crape myrtle pruning

Published 11:27 am Friday, January 21, 2022

The topic of crape myrtle pruning is a subject of a good deal of interest and engenders strong feelings in some. Allegations of “crape murder” are not uncommon.

The dormant period, prior to when new growth begins, is a good time to prune — if pruning is needed — crape myrtles, as well as other plants that flower on new growth. These include chaste tree (vitex), rose-of-Sharon (althea), and American beautyberry. On the other hand, wait until after plants like azaleas, mophead (“French”) hydrangeas, and bridal wreath spirea have finished flowering to prune them, since they bloom on the previous season’s growth.

There is no one right way to prune a crape myrtle, or any other plant. There are certainly scientific principles to be aware of when pruning, but much about pruning ornamental plants depends on your preferences.

Crape myrtles do not necessarily need to be pruned every year. If they’ve been planted in a place where they have enough room to grow to their natural mature size without hitting a house, power line, etc., a lot of pruning can be avoided. (For plants near houses and other buildings, a rule of thumb is to space them half of their expected mature width, plus one foot, from the wall).

One part of training crape myrtles is deciding how many trunks you want. Many varieties of crape myrtle will naturally grow as a shrub, with many shoots arising from the base, if allowed to do so. Three to five trunks are common choices, but this is up to you. You can train it to have a single trunk, or you can let it grow as a shrub without removing any. Regardless, regularly remove shoots that you don’t want. Start doing this when the tree is young to avoid having to make larger cuts later.

Many people also prefer to remove shoots growing from the lower parts of the trunks, to raise the canopy of the plant and contribute to a tree-like rather than shrub-like appearance. Likewise, start doing this early in the life of the plant.

If you must prune to reduce size, try to avoid making cuts in the middles of branches or trunks. If you do this, multiple new sprouts will likely arise just under where the cut is made, and you may need to make more cuts again soon.

One option is to cut individual limbs back to their points of origin, just outside of what’s called the branch collar. (Avoid leaving a stub or making what’s called a flush cut, which removes part of the branch collar.) This is called a thinning cut.

Another option is to make cuts just above where a lateral (side) branch emerges from the limb you’re cutting. A rule of thumb is to cut back to a branch that is no smaller than one-third to one-half of the diameter of the part that you’re removing.

If you do choose to make cuts in the middles of shoots, try not to do this on shoots larger than the diameter of a pencil. This is just a rule of thumb — as a general principle, smaller wounds are better than larger ones.

Remove dead or diseased limbs, as well as ones that are rubbing against other branches. You may prefer to make a few additional thinning cuts within the canopy, to open it up some.

Let me know if you have questions.

Dr. Mary Helen Ferguson is an Associate Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu, 985-839-7855 (Franklinton) or 985-277-1850 (Hammond).