Crape myrtle

Identification and origin

Lagerstroemia indica belongs to the family Lythraceae. Despite its name, India is not part of its native range: it grows wild from the Himalayas to Myanmar, Vietnam, southern China, and Taiwan, and it has naturalized in the southeastern United States.

It is a fast-growing deciduous shrub or small tree, often multi-trunked with a vase-shaped crown; depending on the cultivar, it reaches 6–30 ft tall. Its 1–3 in leaves emerge tinged with red, turn dark green and glossy in summer, then yellow, orange, or red in fall. The thin, smooth bark peels away in patches to reveal shades of beige, cinnamon, or gray.

The flowers, 1–2 in across, have six ruffled petals that look like crepe paper. They form panicles 6–18 in long at the tips of the current season’s shoots, from summer into early fall: rose to red in the wild species, and white, pink, red, or lavender in cultivated varieties. Brown capsules then hang on through winter.

Many plants sold today are actually hybrids with L. fauriei, a Japanese species, selected at the U.S. National Arboretum for disease resistance and bark: ‘Natchez’ (white, cinnamon bark), ‘Muskogee’ (lavender), ‘Tuscarora’ (coral pink), and ‘Acoma’ (white). ‘Catawba’ (purple), ‘Cherokee’ (bright red), and ‘Carolina Beauty’ (red) are L. indica. Dwarf series such as Razzle Dazzle stay around 2–4 ft.

Light

Full sun is essential: at least six hours of direct sun a day. In shade it blooms poorly and suffers more from powdery mildew and sooty mold, and large nearby trees also compete with it for water. Choose an airy spot that is sheltered from winter winds. Where frost is common, plant it against a warm wall facing south or west.

Watering

Once established it tolerates drought well, but it needs regular watering for about two years after planting: water deeply at planting time, then whenever the soil surface dries out and there has been no rain. On an established plant, a deep soaking during dry spells in the blooming season improves flowering.

Water at the base rather than over the foliage: leaves that stay wet encourage powdery mildew. A 3–5 in layer of mulch keeps the soil moist and insulates roots against both cold and heat. In a container the mix dries out much faster: check it often with a finger and keep it moist but never soggy, even in winter.

Potting mix

In the ground it adapts to clay, loam, sand, or rocky soil, acidic or alkaline, as long as water drains: poorly drained soil leads to root rot. Dig a hole twice as wide as the root ball, set the plant no deeper than it grew in the nursery, and backfill with the original soil: amendments placed only in the hole keep roots there instead of encouraging them to spread into the surrounding soil.

In a container, use a soil-based potting mix heavy enough to keep the plant stable, in a pot with plenty of drainage holes. A light complete fertilizer in spring and summer is enough: too much nitrogen reduces flowering and produces soft shoots that are prone to winter injury.

Temperature

A lover of hot summers, it is grown in the ground in USDA zones 6a to 9b; in the coldest of these zones, the top growth can be damaged by winter. In a very severe winter the stems sometimes die back to the ground, but the roots resprout, although it can take years for the plant to regain its former size.

In a container the roots are far more exposed: protect the plant when temperatures approach 23 °F by wrapping the pot in bubble wrap or burlap, or overwinter it in a cool greenhouse. Do not prune in early fall: pruning forces new growth and delays dormancy, and a plant that is not fully dormant can be killed by a hard freeze.

Repotting

Dwarf and semi-dwarf varieties are the best choices for containers. Do not put a young plant in an oversized pot: move it up gradually, in spring, to a final container at least 18 in across. Each spring, scrape away about 2 in of mix from the surface and replace it with fresh mix blended with slow-release fertilizer.

Pruning

Crape myrtle flowers on new growth and does not need pruning to bloom. Cutting the main limbs back every year, nicknamed “crape murder,” is a common mistake: it produces thin shoots that droop under the weight of the flowers, increases suckering, draws aphids to the soft new growth, and encourages powdery mildew. A better approach is to choose a variety that fits the space at maturity.

If pruning is needed, do it in late winter, before growth begins. To train a tree form, keep three to five strong trunks, remove lower limbs up to one-third or one-half of the plant’s height, then take out branches that cross or grow toward the center, cutting just outside the branch collar. Pull suckers while they are still soft. On smaller plants, removing spent flowers right away often triggers a second bloom.

Propagation

Cuttings are the easiest method. In summer, take semi-hardwood cuttings from the current season’s growth with three or four nodes, keeping a few leaves; rooting hormone is generally unnecessary. Stick them in a well-drained medium, in shade, inside a clear plastic bag: they root in three to four weeks. Softwood cuttings in late spring also work. Move the young plants to their permanent spot in fall or winter.

Seed is sown in spring at about 50 °F. Patented cultivars cannot be legally propagated while the patent is in force.

Common problems

• White powdery coating on leaves, shoots, and buds: powdery mildew, mostly in spring and fall, with warm days, cool nights, and humid air. Infected buds might not open. Full sun, good air circulation, and resistant varieties are the best prevention.
• Yellow spots, then leaf drop in late summer: Cercospora leaf spot, favored by warm, wet weather.
• Yellow-green aphids under young leaves, sticky honeydew, black coating: aphids and sooty mold. Let lady beetles, lacewings, and hover flies do their work, or knock the aphids off with a strong spray of water.
• White or gray waxy crusts on trunks and branches: crapemyrtle bark scale, a pest introduced from Asia; crushed, it releases a reddish fluid. Gently brush affected areas and inspect nearby susceptible plants, including pomegranate and fig.
• Poor flowering: shade, excess nitrogen, competition from nearby trees, or lack of water.
• Under glass: spider mites and whiteflies.

A single symptom can have several causes: look at light, watering, drainage, and insects together before acting.

Toxicity

Crape myrtle is listed as non-toxic to dogs, cats, and horses, and no toxicity to people has been reported. Its fallen flowers can, however, stain paving and car paint.