Plant Answers  >  CRAPEMYRTLE - THE BEST LANDSCAPE PLANT FOR TEXAS

CRAPEMYRTLE - THE BEST LANDSCAPE PLANT FOR TEXAS


What is the most versatile plant in the Texas landscape? The one which flowers all summer, is available in different colors, has beautiful bark, has different shapes and sizes from groundcover to shrub to tree, is drought tolerant after it is well established (approximately two years), grows well in alkaline or acid soil, is a fast-growing plant with a long life span, is disease resistant and the foliage displays fall color? The answer has to be crape myrtle.

Crape myrtle (Lagerstroemia species) is a handsome, summer-flowering, deciduous (loses its leaves) tree-shrub-groundcover. It has been called the lilac of the south. The most common species in the United States is Lagerstroemia indica. It is native to China and Korea but is naturalized in the Southern U.S. L. fauriei, native to Japan, is another species found in the United States. Hybrids of the two species generally result in excellent selections as pictured and described at:
http://aggie-horticulture.tamu.edu/plantanswers/trees/crapemyrtle/crape_myrtle_varieties.html

The crape myrtle is valued mainly for its long period of striking summer flowers. These showy flowers may be shades of white, pink, red or lavender. Bloom time varies, depending on the variety. Large clusters appear on the tips of new branches beginning in early summer and continue into fall. After flowers fade and fall from the tree, the fruit (small brown capsules) can be cut from the plant to stimulate more bloom in 30-45 days. Fruit capsules should not be removed after September.

The attractive, exfoliating bark peels away to expose a trunk which ranges in color from many handsome shades of brown to gray. This bark is especially noticeable in the winter months when the tree is leafless.

Fall leaf color ranges from yellow to orange and red. Although the same plant may display leaves of several colors, the white-flowered types often have yellow fall color, and the pink and red flowered types show yellow, orange and red leaf color in the fall.

The crape myrtle can be planted as a specimen or in groups, and looks attractive when a ground cover is planted under and around the plant; the dark green of the groundcover contrasts well with the handsome bark. It adapts well to confined spaces, and is, therefore, well-suited for small areas close to sidewalks or parking lots, and can provide shade in deck and patio areas. The plant typically develops several main stems. These multi-trunk crape myrtles are more desirable than single stem plants in landscape plantings.
Crape myrtle can be a low-maintenance plant, and the best way to ensure this is to choose the cultivar that best suits your landscape needs before planting. There are many new cultivars in different sizes and colors. The dwarf (3 to 6 feet) and semi-dwarf (7 to 15 feet) selections now available make it easy to choose the right size plant for a certain space. As varieties are now available in a wide range of growth heights, certain selections can be used under utility lines without fear of interfering with these lines.

The ideal planting site is in well-prepared, well-drained soil, with full sun exposure and good air circulation. Crape myrtles planted in partial or full shade will have reduced flowering and increased disease susceptibility.

Heavy nitrogen applications cause the plants to flower less and produce shoot and leaf growth that may be subject to winter injury. Light applications of a complete, slow-release fertilizer such as 19-5-9 in early spring should be made just before new growth begins. A general recommendation of 2 pounds (two cupfuls) of the slow-release fertilizer per 1,000 square feet of root area is sufficient for most trees and shrubs. This can be repeated again in the late fall. The number of square feet in the root area is determined by the branch spread of the tree.

Severe pruning of crape myrtles has become a common practice to maintain shrub size. This ruins the natural, graceful effect of the plant. Many dwarf and semi-dwarf cultivars are now available, making it possible for the homeowner to have the desired plant size while maintaining the natural branching effect. The practice of chopping off the tops of crape myrtle has become very commonplace. Many people believe that it is required to promote flowering; some prune because the plant is too large for the space provided; others see their neighbors doing it and feel the need to follow suit. There are some instances in which heavy pruning is necessary, but light pruning is usually all that is needed. The type and amount of pruning depends on the desired shape and size of the plant.

Crape myrtle does not require heavy pruning to promote bloom. Flowers are produced on new growth. It will produce flowers without any pruning, although it will produce larger flowers and bloom more profusely if at least lightly pruned. Pruning in late winter or early spring will stimulate vigorous new growth in the spring. For more information on the pruning of crape myrtle, see:
http://aggie-horticulture.tamu.edu/PLANTANSWERS/publications/stopthecrape.html

Powdery mildew fungus caused by the fungus Erysiphe lagerstroemiae is a common problem with crape myrtle. It first appears on new shoots as a whitish powder that later spreads to the surface of leaves, stems, and flowers (a black powder on leaves is caused by sooty mold). Powdery mildew causes leaves, stems and flowers to become distorted and stunted. In severe cases, leaves may drop prematurely and flower buds may fail to open properly. Shady, humid locations and cool nights encourage powdery mildew as does frequent wetting of the foliage by irrigation or rainfall. Powdery mildew is more prevalent in spring and fall. Locating the plant in full sun and providing good air circulation so that wet foliage dries quickly helps prevent powdery mildew, but the best approach is to choose resistant varieties as listed at:

http://aggie-horticulture.tamu.edu/plantanswers/trees/crapemyrtle/crape_myrtle_varieties.html

Crapemyrtle aphid, Tinocallis kahawaluokalani, was apparently introduced into the United States with crape myrtle, its host plant. Crapemyrtle aphids are pale yellow in color with winged adults having black wings and black protuberances. They primarily are found on undersides of leaves and are particularly attracted to new growth. Crapemyrtle aphid is not found on any other commonly grown plant. No aphid species other than crapemyrtle aphid infest crape myrtle.

These insects damage crape myrtle by inserting mouthparts into soft tissue and extracting plant sap. Crapemyrtle aphids can reproduce and develop large numbers rapidly. Heavy infestations distort leaves and stunt new growth.
Sprays of insecticidal soaps or horticultural oils are the most environmentally safe pesticides for controlling crapemyrtle aphids.

During feeding, aphids secrete droplets of a sugary solution called "honeydew." Drops of honeydew fall from the aphids onto leaves and stems below. This sugary solution promotes the growth of sooty mold fungi, Capnodium species. Sooty mold appears as a black staining or powdery coating on leaves and stems (a whitish powder on leaves is symptomatic of powdery mildew). The blackened leaves and stems are often the most obvious sign of aphid infestation.

Although unsightly, sooty mold itself does not directly harm crape myrtle. However, the black fungus shades the leaves and interferes with photosynthesis, potentially reducing the long-term vigor of the plant. Control of crapemyrtle aphid will halt further development of sooty mold. Existing sooty mold on leaves will wear off the leaves through the actions of sun, rain, and wind. Sprays of insecticidal soaps and horticultural oils for control of crapemyrtle aphid also help to loosen and remove sooty mold. See article and images at: http://www.plantanswers.com/mist_from_above.htm and

http://www.plantanswers.com/black_crepe_myrtle.htm

The bark is thin and can be easily damaged by mechanical injury. Mulch around plants to prevent this problem. Vigorous, shallow roots may create problems for healthy growth of underlying plants. Use sturdy ground covers or shrubs to be planted around the crape myrtles.

Many crape myrtles are hybrids of L. indica and L. fauriei, developed at the U.S. National Arboretum in Washington, D.C. These were bred for disease resistance, good flowering and attractive bark. (Disease resistance means that infections are few, do not progress very far or do not occur).

If careful consideration is given to the projected size of the mature plant, a selection can be found that will not outgrow its boundaries and can be allowed to display its graceful beauty with minimal pruning. It is important that tree types are sited where they have a large area to spread. When given an ideal location, these tree types should be allowed to develop their natural style without whacking off their tops.

To develop a tree shape, remove all limbs growing from ground level except the three to five strongest limbs. As the tree matures, remove lower, lateral branches ("limbing up") one-third to halfway up the height of the plant. Remove branches that are crossing or rubbing against each other and shoots growing into the center of the canopy. Make your cuts to a side branch or close to the trunk. Head back wayward and unbranched limbs. As it grows taller, remove lower branches as needed. Remove any future growth from the ground to retain the desired tree shape. This basal sprouting may occur whether the tree is being pruned or not. Pull these out when succulent instead of pruning them.

You may feel the need to improve the appearance by removing the seed heads in late winter or early spring before growth begins. This is recommended only if they are within reach. Once this becomes a tall, mature plant, allow nature to take its course - the seeds will drop, the plant will bloom, and the natural grace of the plant has been retained.

Consider all your options when confronted with a large, old crape myrtle in a space meant for a different shaped tree or shrub. To create clearance under the canopy, limb up old trees that have spread their lower limbs where they interfere with people or cars. Limb up above the roof-line of a single story home to clear obstruction of a window or door. Eliminate one of the major trunks if it is leaning too close to a building. Only as a last result should you top a beautiful, old specimen to squeeze it into a confined space.

To keep a crape myrtle at a manageable height, prune moderately by removing all twiggy growth back to lower growing side branches. This will give the plant a more uniform appearance. As mentioned earlier, the best way to maintain a crape myrtle at a particular size is to plant a known cultivar that will mature at the desired height and spread.

If you have a crape myrtle in a spot where you want a low, compact plant, you have two options: (1)Dig it up and plant a new dwarf cultivar that will require little or no maintenance; (2)Prune the stems back to about six inches above the ground each year. Severe pruning will not kill or injure a healthy crape myrtle.

Practice corrective pruning to remove defective or dead branches. This should be done at the time the problem is detected. Otherwise, prune to remove lateral branches, small twigs or branches in the center to create more open space for sun and air movement while the plant is dormant (winter or early spring).

History and Taxonomy
Lagerstroemia species are deciduous shrubs or trees with geographic origins in China, Japan, and other parts of southeast Asia. L. indica has been cultivated as an ornamental for centuries and was introduced to the southern United States over one hundred and fifty years ago. L. speciosa, commonly called Queen's Crape Myrtle, has been popular as a flowering street tree in tropical areas. L. fauriei, L. subcostata and L. limii have been used in breeding programs, and cultivars of L. indica × fauriei hybrids now constitute the most widely grown crape myrtles today. One dwarf tri-species hybrid was named 'McFadden's Pinkie Myrtlette' and has been maintained by Dr. Sam McFadden. It will have use as one of the "Myrtle-ettes" or small crapemyrtles among the Lagerstroemia cultivars. 'Pinkie' was obtained from a cross between on of Dr. Donald Egolf's progeny (L. indica x L. faurei) seedlings from the National Arboretum that was being tested in Florida and a USDA plant introduction from Japan of L. subcostata with very small florets. Other species of Lagerstroemia are used as timber in their native ranges in Asia.

The scientific name, Lagerstroemia, was coined in 1759 by Carl Linnaeus, who described and named the plant in honor of Magnus von Lagerstroem, an avid naturalist and director of the Swedish East Indies Company. Crape myrtle derives its common name from its crepe-like, crinkled petals, and the resemblance of its leaves to the true myrtle, Myrtus communis. "Crape myrtle" is a peculiarly-American term. Elsewhere in the world, "lagerstroemia" is often used as the common name for crape myrtle.

Crape myrtle is valued as a landscape plant for its prolific summer flowers, heat and drought tolerance, and year-round landscape interest. Flowering begins as early as May in some cultivars and continues into the fall. Each 6- to 18-inch cluster of flowers (or panicle) develops on the tips of new growth and is composed of hundreds of 1-to 2-inch flowers. Color ranges include shades of purple, lavender, white, pink and red, including "true" red, a relatively recent development. Some cultivars have bicolor flowers (two colors on each petal), some cultivars have flower colors that fade with age or certain environmental conditions, and other cultivars have panicles composed of a mix of flower colors.

Many Lagerstroemia fauriei and hybrid cultivars feature beautiful, colorful bark. Strips of bark peel off in early summer to reveal mottled new bark ranging in color from pale cream to dark cinnamon to rich brown to bright orange. The bark color gradually fades over winter until it peels again the next summer.

Leaves on many of the Lagerstroemia indica cultivars are rounded or spoon-shaped and up to 3 inches long. Most hybrid cultivars have lance-shaped leaves up to 5 inches long and 3 inches wide while other species have even larger leaves. Leaves are often tinged red in the spring and turn dark green by summer. Several cultivars are known for new growth that is bronze, red or burgundy and some cultivars are claimed to have burgundy-colored foliage all summer. In temperate climates, foliage may turn brilliant yellow, orange or red in autumn.

When the leaves fall in winter, crape myrtle becomes a living sculpture. The trunk and branches of tree-form plants have an attractively gnarled, sinuous character with smooth bark.

Crape myrtle has low salt tolerance, so it should not be irrigated with saline water or used near the coast unless it is well-protected from saline conditions.

Crape myrtle transplants easily. Best results occur if container-grown crape myrtles are planted during early summer when in active growth. Bare root or balled-and-burlapped crape myrtles should be moved and planted while dormant. Plants should be mulched to a depth of 3 inches.

Newly planted crape myrtle should be irrigated regularly for the first few weeks to aid in establishment. Trees with a trunk diameter greater than 1 inch benefit from regular irrigation for several months. Crape myrtle is very drought tolerant once established but moist soil or irrigation promotes growth. Fertilization will stimulate growth of young crape myrtles but established crape myrtles usually do not need fertilizer because root systems extend into lawns where they can absorb nutrients from applications of lawn fertilizers.

Young crape myrtles characteristically develop multiple stems. If a crape myrtle is to be grown as a small tree, the smallest stems should be removed, leaving one main stem for a single-trunk specimen or 3 to 5 main stems for a multi-trunk tree.

Crape myrtle generally requires little pruning. "Suckers" or water sprouts may develop along the lower portions of main stems or from roots. These should be removed when using crape myrtles as trees. Small twiggy growth on disease-susceptible shrub and tree forms should be thinned out from underneath and within the canopy. This keeps the trunk clean to allow air circulation and help prevent powdery mildew disease. Dwarf crape myrtles periodically grow tall shoots that must be removed to maintain the planting as a groundcover. Shoots of some dwarf cultivars occasionally die to the ground over winter, and dead wood should be removed in the spring.

If pruning is necessary to improve plant shape or form, prune crape myrtle anytime after the leaves have fallen. However if plants are pruned too early in the fall, new growth may emerge and be killed by the first freeze. Plants are easy to prune while dormant since the branch structure is readily visible without foliage. Pruning while plants are dormant also will not interfere with flower bud formation since crape myrtle flowers form on new growth. Avoid annual or frequent hard pruning. Severe pruning can induce excess vegetative growth, basal sprouting, and fewer, but larger, flower panicles. It also spoils the beautiful winter branch structure on crape myrtle trees.

Tip pruning to remove old flower clusters will promote recurrent blooming but is not practical for large plants or low maintenance landscapes. Tip pruning is largely unnecessary on many newer cultivars that naturally repeat-bloom, but tip pruning may enhance recurrent bloom of older L. indica cultivars.

Secondary pests of crape myrtle include metallic flea beetle (Altica species), wax scale (Ceroplastes floridensis), Cercospora leafspot (Cercospora lythracearum) and mushroom root rot (Armillaria tabescens).

Crape myrtle can be propagated vegetatively by softwood, semi-hardwood, hardwood, or root cuttings. Softwood and semi-hardwood cuttings root easily when taken in spring or summer. Hardwood cuttings from dormant plants also root easily, although use of rooting hormone improves rooting percentages. Root cuttings may be dug in early spring and planted in the greenhouse. Root cuttings root inconsistently.

Seed capsules ripening in the fall may be collected, dried, and stored in sealed containers. No seed pre-treatment is necessary and seeds will germinate within 3 weeks after sowing. Best growth results when seeds are sown during the lengthening days of spring. Flower, bark and growth characteristics of crape myrtle seedlings vary tremendously.

Many cultivars of crape myrtle have been developed by private individuals, nurseries and public institutions. In 1962, the U.S. National Arboretum in Washington D.C. began a crape myrtle breeding project with Lagerstroemia indica. Major advances occurred when L. subcostata and L. fauriei were introduced into the breeding program in 1966. The resulting hybrids were highly ornamental and resistant to powdery mildew. As a result of the late Dr. Donald Egolf's efforts, the U.S. National Arboretum has released over 24 selected for cold hardiness, for resistance to powdery mildew, and for varying heights, habits, flower colors, fall foliage colors, and bark characteristics. All U.S. National Arboretum cultivars have Native American names.
Complete descriptions of all Egolf releases at:

http://www.usna.usda.gov/Research/Herbarium/Lagerstroemia/Checklist_A.html

The U.S. National Arboretum is continuing Dr. Egolf's work, and many other individuals also have joined the ranks of crape myrtle breeders. Dr. Carl Whitcomb, Dr. Michael Dirr and Dr. Cecil Pounders currently operate prominent crape myrtle breeding programs. Much more about crape myrtles can be found at:

http://aggie-horticulture.tamu.edu/plantanswers/trees/crapemyrtle

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References
Byers, David. 1999. Personal communication. Byers Nursery Company, Inc., Huntsville, AL.

Byers, David. 1997. Crapemyrtle: A Grower's Thoughts. Owl Bay Publishers Inc., Auburn, AL.

Davy, John. 1999. Personal communication. Panhandle Growers, Inc., Milton, FL.

Dirr, Michael A. and Charles W. Heuser, Jr. 1987. The Reference Manual of Woody Plant Propagation. Varsity Press, Inc., Athens, Georgia. 239 pp. Pp. 144-145.

Egolf, Donald R. and Anne O. Andrick. 1978. The Lagerstroemia Handbook/Checklist. American Association of Botanical Gardens and Arboreta, Inc. 72 pp.

Knox, Gary W. and Jeffrey G. Norcini. 1991. "Lagerstroemia cultivars under evaluation at the NFREC-Monticello." Proc. Fla. State Hort. Soc. 104: 346-347.

Mizell, Russell F., III and Gary Knox. 1993. "Susceptibility of crape myrtle, Lagerstroemia indica L., to the crapemyrtle aphid, Tinocallis kahawaluokalani (Kirkaldy) in north Florida." Journal of Entomological Science 28(1): 1-7.

Pooler, Margaret and Ruth Dix. 1999. Personal communication. U.S. National Arboretum, Washington, D.C.

Westcott, Cynthia. 1971. Plant Disease Handbook, third edition. Van Nostrand Reinhold Company, New York. 843 pp. Pp. 293-298 and 405-406.

 


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