Lagerstroemia x 'Sioux' Sioux Crape Myrtle

Introduction

A long period of striking summer flower color, attractive fall foliage, and good drought-tolerance all combine to make crape myrtle a favorite small tree for either formal or informal landscapes. It is highly recommended for planting in urban and suburban areas.

General Information

Scientific name: Lagerstroemia x 'Sioux'

Pronunciation: lay-gur-STREE-mee-uh

Common name(s): 'Sioux' crape myrtle

Family: Lythraceae

Plant type: shrub

USDA hardiness zones: 7 through 9 (Figure 3)

Planting month for zone 7: year-round

Planting month for zone 8: year-round

Planting month for zone 9: year-round

Origin: not native to North America

Invasive potential: not known to be invasive

Uses: specimen; near a deck or patio; border; container or above-ground planter; trained as a standard; small parking lot islands (< 100 square feet in size); medium-sized parking lot islands (100–200 square feet in size); large parking lot islands (> 200 square feet in size); narrow tree lawns (3–4 feet wide); medium-sized tree lawns (4–6 feet wide); wide tree lawns (>6 feet wide); recommended for buffer strips around parking lots or for median strip plantings in the highway

Availability: generally available in many areas within its hardiness range

Description

Height: 15 to 20 feet

Spread: 10 to 15 feet

Plant habit: oval

Plant density: moderate

Growth rate: moderate

Texture: medium

Foliage

Leaf arrangement: alternate

Leaf type: simple

Leaf margin: entire

Leaf shape: oblong; obovate

Leaf venation: pinnate

Leaf type and persistence: deciduous

Leaf blade length: 2 to 4 inches

Leaf color: green

Fall color: purple

Fall characteristic: showy

Flower

Flower color: pink

Flower characteristic: summer flowering

Fruit

Fruit shape: oval

Fruit length: 0.5 to 1 inch

Fruit cover: dry or hard

Fruit color: brown

Fruit characteristic: persists on the plant

Trunk and Branches

Trunk/bark/branches: showy; no thorns; can be trained to grow with a short, single trunk

Current year stem/twig color: reddish

Current year stem/twig thickness: thin

Culture

Light requirement: plant grows in full sun

Soil tolerances: slightly alkaline; clay; sand; acidic; loam

Drought tolerance: high

Soil salt tolerances: unknown

Plant spacing: 36 to 60 inches

Other

Roots: usually not a problem

Winter interest: plant has winter interest due to unusual form, nice persistent fruits, showy winter trunk, or winter flowers

Outstanding plant: not particularly outstanding

Pest resistance: long-term health usually not affected by pests

Use and Management

Available in all shades of white, pink, red, or lavender, the 6- to 12-inch-long clustered blooms appear on the tips of branches during late spring and summer in USDA hardiness zones 9 and 10 as well as summer in other areas. The individual flowers are ruffled and crinkly as if made of crepe paper. The smooth, peeling bark and multi-branched, open habit of crape myrtle make it ideal for specimen planting where its bright red to orange-colored fall leaves add further interest. Most forms of the tree are upright, upright-spreading, or vase-shaped, spreading out as they ascend. Most tree types grow to 20 to 25 feet tall although there are more dwarf types available. The upright, vase-shaped crown makes the tall-growing selections well-suited for street tree planting.

Pruning should be done in late winter or early in the spring before growth begins because it is easier to see which branches to prune. New growth can be pinched during the growing season to increase branchiness and flower number. Pruning methods vary from topping, to cutting crape myrtle nearly to the ground each spring, to the removal of dead wood and old flower stalks only. Topping creates several long, thin branches from each cut that droop down under the weight of the flowers. This practice disfigures the nice trunk and branch structure. Lower branches are often thinned to show off the trunk form and color. You can remove the spent flower heads to encourage a second flush of flowers and to prevent formation of the brown fruits. Since cultivars are now available in a wide range of growth heights, severe pruning should not be necessary to control size. Severe pruning or topping can stimulate basal sprouting, which can become a constant nuisance, requiring regular removal. Some trees sprout from the base of the trunk and roots even without severe heading. This can be a maintenance nuisance.

Crape myrtle grows best in full sun with rich, moist soil but will tolerate less hospitable positions in the landscape just as well once it becomes established. It grows well in limited soil spaces in urban areas such as along boulevards, in parking lots, and in small pavement cutouts if provided with some irrigation until well established. They tolerate clay and alkaline soil well. However, the flowers of some selections may stain car paint. Insect pests are few, but crape myrtle is susceptible to powdery mildew damage, especially when planted in some shade or when the leaves are kept moist. There are new cultivars (many developed by the USDA) available which are resistant to powdery mildew and aphids.

Many cultivars of crape myrtle are available: hybrid 'Acoma', 14 to 16 feet tall, white flowers, purple-red fall foliage, mildew resistant; hybrid 'Biloxi', 25 feet tall, pale pink blooms, orange-red fall foliage, hardy and mildew resistant; 'Cherokee', 10 to 12 feet, bright red flowers; 'Powhatan', 14 to 20 feet, clear yellow fall foliage, medium purple flowers. The hybrid cultivars 'Natchez', 30 feet tall, pure white flowers, resistant to aphids, one of the best crape myrtles; 'Muskogee', 24 feet tall, light lavender flowers, and 'Tuscarora', 16 feet tall, dark coral pink blooms, are hybrids between Lagerstroemia indica and Lagerstroemia fauriei and have greater resistance to mildew. The cultivar ‘Crape Myrtlette’ has the same color range as the species but only grow to three to four feet high. The National Arboretum releases are generally superior because they have been selected for their disease resistance. These releases may prove more resistant to powdery mildew in the Deep South, although further testing needs to be done to confirm this.

Propagation is by cuttings or seed.

Pests and Diseases

Aphids often infest the new growth causing an unsightly but harmless sooty mold to grow on the foliage. Heavy aphid infestations cause a heavy black sooty mold, which detracts from the tree's appearance.

Powdery mildew can severely affect crape myrtle. Select resistant cultivars and hybrids to avoid this disease. Leaf spots are only a minor concern and do not require treatment.