January 14, 2008

Pruning Crape Myrtles

Pam Brown,Urban Horticulture Extension Agent

By Pam Brown
Urban Horticulture Extension Agent

Crape myrtle (Lagerstroemia indica) is a small tree that prefers hot, sunny climates. It is well adapted to our climate here in Pinellas County. Once well established, these trees are extremely drought tolerant and have low fertilizer requirements. Crapes grace us with lovely blooms in the summer. And, if pruned or trained properly, the bare trunk and branches are very sculptural after loosing leaves in early winter.
bad crape myrtle pruning
The common practice of chopping off the tops of crape myrtles is a severe pruning practice that induces excess vegetative growth, promotes sprouting at the base of the plant, creates unnatural branch structure, and results in larger but much fewer flowers. Many prune this way because the plant is too large for the space where it is planted or they see their neighbor’s trees pruned this way and feel that this must be the correct way to prune. There is also the misconception that this type of pruning is necessary to promote blooming. In actuality, light corrective pruning is all that is needed.

The best way to assure that the crape myrtle that you have planted will not grow too large for the space provided is to choose a cultivar for the mature size it will become. There are dwarf, semi-dwarf, intermediate and tree forms of crape myrtles. The University of Florida/IFAS publication Crape Myrtle in Florida ( lists cultivars by name, size, color of blooms, and disease resistance.

Flowers are produced on new growth and crape myrtles will bloom without any pruning. Pruning can produce blooms of larger size, but there will usually be fewer of them. Removing seedpods as they form during the summer can stimulate another flush of blooms before fall. Full sun is required for best flowering. So, crape myrtles planted in shade will not develop many blooms.

Pruning should be done in January or early February before new growth starts. To allow the plant to develop into the small graceful tree that it is destined to become, select one to several strong trunks originating from the ground and prune off any weaker remaining stems at ground level. As the tree grows, remove lateral branches to one-third or halfway up the plant. Also remove any branches in the developing canopy that are crossing or rubbing another branch. This will develop an open canopy, which allows air circulation that will discourage fungal disease. Any broken or dead branches should also be removed. All cuts should be made either to the trunk or to a side branch that is facing out from the center of the tree. These are called thinning cuts that should not produce a heavy flush of dense growth in the canopy. In addition, the sprouts (suckers) that grow up from the base of the tree should be pulled out while they are still green a succulent.

There are lovely examples of properly pruned crape myrtles in several locations on the grounds of the Florida Botanical Gardens.

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