LSU AgCenter horticulturist
HAMMOND — A poor horticulture practice in Louisiana and across the South involves one of our most beloved landscape trees. Each year, crape myrtles are pruned improperly. One of the 10 commandments of gardening should be “thou shalt not top crape myrtles.”
Typically, you will see “crape murder” committed in December, January and February, but everyone seems to be in a hurry this year. Crape murder began in September and is continuing at an ever increasing pace. This is alarming and very concerning.
Topping crape myrtle trees is commonly referred to by knowledgeable gardeners as crape murder. This 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. Worse yet, when people prune improperly over several seasons, unsightly, large, swollen knobs form at the point where pruning is done each year.
Crape myrtles need only occasional pruning, in most cases, to obtain the desired landscape effect. But many times these plants are butchered for no good reason.
Crape myrtles are our most popular, small, flowering tree in Louisiana. Why do we improperly prune this beautiful tree this way?
We often encounter gardeners who think they are supposed to prune their crape myrtles severely. 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 severely to bloom well. This is not true. The flower clusters may be larger on topped 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, it actually produces fewer flower clusters.
Sometimes crape myrtles are pruned improperly to create a different shape. A wide selection of crape myrtle varieties is available today. 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. Over time, the new growth will simply grow upright again. So if you want a crape myrtle that will mature in the shape you desire, make sure you choose one that naturally grows that way.
Sometimes gardeners cut back crape myrtles that have grown too large for the location where they were planted. This is fairly common with crape myrtles planted close to a house. Instead of choosing a smaller growing variety that would be appropriate, someone planted a larger type that then began to grow into the gutter and onto the roof.
To salvage the situation, people often begin cutting their trees back. To be effective, this has to be done every year. But it 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 feet to 12 feet, rather than Natchez, which matures at 25 feet 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. 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 you’ve identified.
Examples of appropriate reasons for pruning include eliminating crossed and rubbing branches, removing low-growing branches, 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 around 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 the winter and exceptionally long blooming season in summer, the crape myrtle is rightfully popular here. Make sure you keep yours looking its best.