Crapemyrtle - Flower of the South
Crapemyrtle (Lagerstroemia sp.) is a popular ornamental shrub/tree that would be a wonderful addition to any Mississippi landscape. The colorful flower clusters offer a spectacular sight from early summer through late fall. Although commonly called the “Flower of the South,” the crapemyrtle is native to China.
Crapemyrtles have aesthetic qualities other than their colorful summer flowers. The trunk color is spectacular on many cultivars and ranges from a light green-gray to a dark cinnamon. The bark on some cultivars peels (exfoliates) in long strands, exposing various colors and creating interesting patterns that enhance the winter landscape.
The foliage is another beautiful feature. While green on most cultivars in spring and summer, it offers an array of fall colors ranging from brilliant yellow to deep maroon. Seed pods develop in early fall and remain on the plants all winter, providing contrast with the exposed linear branches. All of these factors combine to make the crapemyrtle an outstanding landscape plant for all seasons.
Crapemyrtles are hardy from USDA Plant Hardiness Zone 7 to Zone 10. North Mississippi is in Zone 7, and the extreme Gulf Coast area is in Zone 9, making the crapemyrtle hardy throughout the state. It is important to note that even though extremely low winter temperatures can sometimes kill plants to the ground, they normally resprout from the roots in the spring.
Crapemyrtles are multi-use plants, which means they can be used as shrubs, small trees, specimen plants, patio/container plants, border plants, and even street trees. Select an appropriate cultivar for each use.
Where to Plant
Crapemyrtles have shallow, fibrous root systems. They grow and flower best in sunny locations with good air circulation and well-drained soil. They can grow in partial shade, but flowering is typically reduced and sometimes nonexistent. Crapemyrtles grow in a wide range of soil types but prefer a soil pH range of 5.0 to 6.5.
When to Plant
Plant container-grown and balled-and-burlapped plants any time of the year. However, planting in the fall or early spring allows time for roots to establish before summer heat arrives. Plant bare-root plants during the winter dormant season.
How to Plant
Prepare a planting hole three times as wide as the root ball. Set the plant in the hole at the same depth it grew in the nursery or container. Then, backfill with the amended soil and water thoroughly. Mulch the planting site with 3 to 4 inches of a mulch product or 6 to 8 inches of pine straw. Taper the mulch or straw to only 1 inch deep at the base of the tree trunk. After planting, stake large plants to prevent top movement and damage to the root system.
If it is necessary to plant in a heavy clay soil, elevate the planting site because crapemyrtle roots do not tolerate wet soils. Also, do not use finely chopped sphagnum peat (peat moss) or sand to amend heavy clay soils. Subsurface drainage tiles, or “French drains,” may be used to remove excess water from the planting area.
If lime is required to raise the pH, mix it thoroughly with the native soil. If a soil amendment is needed, incorporate pine bark or compost into the soil. When planting in sandy soils, adding peat moss helps retain moisture and fertilizer. Thoroughly mix the peat moss with the backfill soil, making sure not to use more than one-third by volume of peat.
Have your soil tested and follow the recommendations provided when fertilizing. If you have not had your soil tested, apply 2 to 4 pounds of a slow-release fertilizer with a 2-1-1 ratio per 100 square feet of bed area. Fertilize individual plants with one-fourth to one-half cup of fertilizer in a circle no closer than 1 foot from the base of the plant. Sprinkle fertilizer uniformly over the area out from the base of the plant, and water the area thoroughly. Fertilize in early spring and again in early summer before the plants begin to flower.
Late fertilization or overfertilization can result in little or no flowering, excessive vegetative growth, and possible winter damage, due to not hardening off.
Pruning can stimulate new growth and increase the number of bloom clusters on the plant. If you choose to do so, prune in late winter or early spring before growth begins. The crapemyrtles will still flower because they bloom on the current year’s wood. Whether the plant will be used as a shrub or a small tree determines the method of pruning. The two basic methods used are thinning and cutting back.
Thinning is the removal of old and weak branches at their points of origin. It is used to open up plants that are pruned to tree form. This does not stimulate prolific growth and leaves the plant with a more natural appearance.
Select one main stem for a single-trunk tree or three to five stems for a multi-trunk tree. Remove all other stems at ground level. Allow the main trunk(s) to reach a height of 5 to 6 feet before branching.
At this height, tip prune to encourage branching. Remove all growth that develops below the desired branch height.
Cutting back is done to maintain the plant at a certain height. Only use this method with shrub forms because it stimulates heavy branching. It also destroys the natural, balanced form of the plant. If the size of the plant is too big for the landscape, the easiest thing might be to cut it back to the ground and let it regrow, or simply remove it.
General Pruning Tips
You can prune fading bloom clusters to encourage the development of additional blooms and to extend the flowering season. Occasionally, heavy bloom clusters and branches have to be removed during the growing season to keep limbs from breaking. Limit this type of pruning to only what is necessary.
Do not prune crapemyrtles in the fall following leaf drop. This may stimulate new growth and make the plants susceptible to winter injury. Also, heavy pruning destroys the natural appearance and form of the plants, which will be obvious during the winter months until growth resumes in the spring.
For more information on pruning crapemyrtles, please see the "Crape Murder" video.
There are crapemyrtle cultivars suited to most all situations in today’s landscapes. Dwarf cultivars are adapted to growing in containers; others are semi-dwarf cultivars, and yet others grow more than 20 feet tall. Some cultivars are upright and narrow in form, while others have a more spreading form. Bark characteristics, flower color, fall color, plant size and shape, and disease resistance have been greatly improved in recent years as the result of private, state, and federally funded breeding programs. See Table 1 for cultivars for Mississippi landscapes. It should be noted that the Ebony series of crapemyrtle is also sold under the Black Diamond product line.
The major disease affecting crapemyrtles is powdery mildew. This fungal disease reduces flower performance and weakens plants by attacking flower buds, growing tips, and young leaves. It is most common when cool nights are followed by warm days and occurs most often in crowded landscapes with poor air circulation. The fungus overwinters in dormant shoot buds, sheltered places on the plant, and diseased plant debris on the ground.
Powdery mildew infection appears as a grayish-white powdery fungal growth. As leaves expand, they become curled and distorted. On older leaves, large white patches of the fungus appear without much leaf distortion. Flower buds covered with the fungus either fail to open or open improperly. The infection may also spread to mature flowers and cause flower blight.
Crapemyrtle cultivars released in recent years with Lagerstroemia fauriei in their parentage are resistant to powdery mildew. Cultivar selection is an effective way to control the disease. These cultivars are noted in Table 1.
Cultural methods for controlling powdery mildew involve sanitation procedures and applying fungicides. In the fall, remove and destroy all diseased twigs. In late winter, proper pruning will improve air circulation and reduce the possibility of disease development.
Begin applying recommended fungicides in the spring when growth begins and immediately after the first sign of disease infection. You may also apply fungicide during the flowering period to prevent blossom blight. It is best to alternate applications of a systemic fungicide with one of the protectant fungicides. Use sulfur only at temperatures below 85°F to avoid leaf burn.
More about powdery mildew and fungicides to control it can be found in Extension Information Sheet 1666 Powdery Mildew on Crapemyrtles.
Sooty mold is a black, powdery coating that develops on leaves and twigs during cool, moist, cloudy weather. Several causal fungi grow in the sugary honeydew deposited on the plants by small sucking insects, such as aphids and white flies. If you control the feeding insects that produce the honeydew, you can control sooty mold.
The fungi that cause sooty mold do not attack the plants but derive nutrients from the honeydew deposited by the insects. Although sooty mold does not directly attack crapemyrtles, its presence destroys their beauty and can weaken the plants by shading the leaves from sunlight. Heavy infestations of insects that secrete honeydew weaken crapemyrtle plants.
Several insecticides are approved for use on crapemyrtles to control sucking insects. More about sooty mold can be found in Extension Information Sheet 1938 The Plant Doctor: Sooty Mold and Publication 2369 Insect Pests of Ornamental Plants in the Home Landscape.
This disease causes the leaves to fall off the crapemyrtle and is most common in late summer. Leaves will have black spots and may turn reddish or yellow, then fall off. The black spot is the fungus. Spraying is seldom needed unless the crapemyrtle is in a high visibility area. Leaf removal and destruction is the best management tool for this disease.
Publication 2007 (POD-10-15)
Revised by Jeff Wilson, PhD, Regional Horticulture Specialist, North Mississippi Research and Extension Center, from an earlier edition by David Tatum, PhD, former Extension Horticulturist; Alan Henn, PhD, Extension Plant Pathologist; and Blake Layton, PhD, Extension Entomologist.