Crape myrtles need full sun in order to perform the best, grow the best and bloom the best. This means eight hours or more of direct sun daily. Less than eight hours of sunlight daily isn’t sufficient for ideal crape myrtle performance. Many of us underestimate the amount of sun that our landscape receives, so check sun patterns in the morning, during the middle of the day and during late afternoon to determine how much sunlight your landscape receives.
Soil pH is important for crape myrtles, but it may not be as important as it is for some of our other landscape plants. Crape myrtles like a soil pH of 6.0-6.5. This is considered slightly acid. Do not guess on soil pH — soil test. You can lower the soil pH with sulfur products and raise the pH with lime products. But always do this based on the results of a soil test.
When it comes to pruning, February is the time to prune crape myrtles. But your particular crape myrtle may not need to be pruned. You should prune these trees to maintain a natural shape or to thin out branches to allow light into the canopy. Do not top or “hack off the top” of crape myrtle trees. This is often referred to as “crape murder.” Major pruning to reduce height is not recommended.
Fertilization is very important for crape myrtles. To maximize spring growth and the resultant summer bloom, crape myrtles should be fertilized in early spring just prior to new growth commencing. A fertilizer like 8-8-8 or 13-13-13 will work fine and is recommended for crape myrtles. It is better to place fertilizer in drilled holes in the ground (about 8-inches deep) than to just scatter fertilizer on top of the ground. You can fertilize later in the spring and in the summer, but the plants won’t benefit as much as when fertilizer is applied in late winter to early spring.
Mulching is, unfortunately, incorrectly done in many residential and commercial landscape plantings. When you mulch, go “out” instead of “up.” You may see mulch piled high around the base of trees. Don’t do this. Spread mulch out under the branches and use pine straw, pine bark or wood chips to a depth of 2-3 inches and refresh the layer as needed. Keep mulch off the trunk.
One problem that is frequent on crape myrtles is insect damage. Actually, most insects do not do much damage except for aphids that may feed on the new shoot growth in the spring. White flies are also sometimes a problem on crape myrtles. Left unchecked, these insects will release bodily fluids onto the foliage, and the resultant honeydew leads to sooty mold on the leaves. This is the black discoloration that occurs normally in the early summer through fall months. If you control the insects, no sooty mold will develop.
Popular crape myrtle varieties in Louisiana include Natchez, Muskogee, Tonto, Acoma and Sioux. Garden centers have the best availability of crape myrtles in late spring and early summer.
All of the practices outlined here will help your crape myrtles be successful long-term in the landscape.
Visit LaHouse in Baton Rouge to see sustainable landscape practices in action. The home and landscape resource center is near the intersection of Burbank Drive and Nicholson Drive (La. 30) in Baton Rouge, across the street from the LSU baseball stadium. For more information, go to www.lsuagcenter.com/lahouse or www.lsuagcenter.com/lyn.