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Prune Crape Myrtles Properly
by Dan Gill
by Dan Gill

email: dgill@agcenter.lsu.edu

Dan Gill earned B.S. and M.S. degrees in horticulture from Louisiana State University in Baton Rouge, and is an Associate Professor in Consumer Horticulture with the LSU AgCenter.

He is the spokesperson for the LSU AgCenter’s Get It Growing project, a statewide educational effort in home horticulture utilizing radio, Internet, TV and newsprint. Gardeners throughout Louisiana read his columns in local newspapers, watch his gardening segments on local TV stations and listen to him on local radio. In the New Orleans area, Dan appears weekly on the Channel 4 Morning News, writes a weekly gardening column for The Times-Picayune and hosts the Saturday morning WWWL Garden Show, a live call-in radio program.

Dan is co-author of the Louisiana Gardener’s Guide and author of Month-by-Month Gardening in Louisiana. His “South Louisiana Region Report” and “Only in Louisiana” columns appear monthly in the Louisiana Gardener Magazine.


February 10, 2013

Now is an appropriate time to prune summer-flowering trees and shrubs. This includes such trees as crape myrtles, vitex, pomegranate, mimosa, tung tree, elderberry and parkinsonia, and shrubs such as abelia, buddleia, althea, hibiscus, tibouchina, indigo, Turk’s cap, Confederate rose, oleander, fire bush, duranta, Mexican heather, buttonbush, and thryallis.

Especially in the case of trees, pruning should generally be done to enhance their natural shape while correcting any problems.

One of the most abused trees in Louisiana’s residential and commercial landscapes is the crape myrtle. Crape myrtles need occasional pruning to obtain the desired landscape effect, but many times these plants are “butchered” for no good reason.

An unfortunate trend in crape myrtle pruning is to “lop off the tops,” which results in a crew-cut appearance. The lush growth that occurs at these cut sites appears vigorous but is actually structurally weak and is more susceptible to fungus diseases such as powdery mildew. And when pruning is conducted improperly over several seasons, unsightly large, swollen knobs form at the point where pruning is done each year.

There is not another small flowering tree used in Louisiana landscapes that is treated this way. Why should we do it to crape myrtles?

The method of cutting back the main branches of a tree to the same spot every year is called pollarding. This pruning method is used on some types of trees in certain situations and tends to be more common in Europe than in America. A gardener should understand, however, that the life of crape myrtle is shortened and the natural beauty of the tree is destroyed by this pruning technique. If a gardener understands this and still decides that pollarding creates the appearance they desire for their trees, well, that’s their choice.

But I often encounter gardeners who have somehow gotten the idea that they are supposed to prune their crape myrtles that way. Nothing could be further from the truth. For the overwhelming majority of us, enhancing the natural shape of our crape myrtles is most appropriate.

Some gardeners have been told that crape myrtles need to be pruned that way to bloom well. This is not accurate. The flower clusters may be larger on pollarded trees. But the added weight on the ends of long branches causes them to bend over awkwardly, especially after rain. And since the tree is smaller, you actually get fewer flower clusters.

Sometimes crape myrtles are pruned improperly in an effort to create a different shape. A wide variety of crape myrtle varieties are available today, and as you look around area landscapes, you will see great diversity among them. Some grow tall and upright like a vase, while others are shorter and spreading, more like a mushroom.

You cannot make an upright-growing crape myrtle grow in the shape of a mushroom by cutting it back. The new growth will simply grow upright again over time. So if you want a crape myrtle that will mature the shape you desire, make sure you choose one that naturally grows that way.

I understand why people cut back crape myrtles that are too large for the location where they were planted. This is commonly seen with crape myrtles planted close to a house. Instead of choosing a smaller-growing variety that would be appropriate, someone chose a larger type that begins to grow into the gutter and roof. In an effort to salvage the situation, people often begin cutting back their trees. To be effective, this has to be done every year and, again, ruins the natural beauty of the tree. This is added work that could have been avoided by planting a smaller-growing crape myrtle in the first place.

For instance, if you want a white-flowering crape myrtle planted at the corner of your house, it would be more appropriate to select Acoma, which matures at 10 to 12 feet, than Natchez that matures at 25 to 30 feet.

To prune a crape myrtle properly, first decide if it needs to be pruned. As with any pruning project, you must have a specific purpose in mind before you begin. In other words, if you can’t come up with a good reason to prune your tree – leave it alone. If you do see something that calls for pruning, study the tree carefully and determine what needs to be pruned to accomplish the specific purpose.

Examples of appropriate reasons for pruning include eliminating crossed and rubbing branches, removing branches that are too low, removing weak, thin branches from the inner part of the tree, trimming off old seed pods, creating a shapelier tree and keeping suckers removed from the base of the trunk.

Avoid cutting back or shortening branches larger than your finger, although cutting larger branches back to a side branch or to the trunk when needed is fine.

With its smooth, muscular trunks, peeling bark, filigree of leafless branches in winter and exceptionally long blooming season in summer, the crape myrtle is rightfully popular here. Make sure you keep yours looking its best.

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