Culture
Best grown in average, medium moisture, well-drained soils in full sun. Does well in loamy, clay soils with good drainage. Benefits from a slow release fertilizer. Overly fertile soils tend to produce lush foliage growth at the expense of flowering with somewhat increased susceptibility to winter injury. Water roots deeply, particularly in dry spells, but avoid wetting the foliage. Plant in protected locations and apply a winter mulch. Growing crape myrtles in the St. Louis area can be tricky because the above ground branches often die to the ground in winter, particularly when temperatures dip below -5 degrees F. Above ground branches are considered to be winter hardy to USDA Zone 7, whereas roots are usually but not always hardy to USDA Zone 5. In the St. Louis area (Zone 6a), some gardeners prefer to grow these plants in somewhat the same manner as buddleias (butterfly bushes) by cutting all stems back to 8” in early spring each year. Roots will sprout new stems which typically grow 2-4’ tall (sometimes more) by the end of the growing season. Flowers appear on the new wood. It is also an option in St. Louis to grow these plants as woody shrubs by pruning them back to live wood in spring at the time new foliage begins to appear (in somewhat the same manner as with some shrub roses). With protection, top growth will survive some winters, but may still suffer significant injury or die to the ground in harsh winters.
Noteworthy Characteristics
Lagerstroemia indica, commonly known as crape myrtle, is an upright, wide-spreading, multi-stemmed, deciduous shrub or small tree in the loosestrife family. It typically grows to 15-25’ tall. It is native from the Himalayas through southern China, southeast Asia and Japan, but has naturalized in the U.S. from Virginia to Arkansas south to Texas and Florida. An additional common name is Lilac of the South in reference to its popularity in southern gardens (USDA Zones 7-9). Key ornamental features include long bloom period, exfoliating bark and superb fall color. Terminal, crepe-papery inflorescences (to 6-18” long) of showy flowers with crimped petals bloom in summer (sometimes to frost) on upright branches. In the wild, flowers are typically rose to red. Cultivated varieties have expanded the flower color range to include white, pink, mauve, lavender and purple. Alternate to sub-opposite, thick and leathery, privet-like, elliptic to oblong leaves (to 3" long) emerge light green often with a tinge of red, mature to dark green by summer and finally turn attractive shades of yellow-orange-red in fall. Flowers give way to round seed capsules which often persist well into winter. Smooth pale pinkish-gray bark on mature branches exfoliates with age. In the St. Louis area where winter injury can be a problem, plants will typically grow to 6-10’ tall. In the deep South, plants will grow much taller if not pruned back. Straight species plants are not sold in commerce. A multitude of named cultivars from dwarf to tree size have been introduced over the years, many of which are hybrids between L. indica and L. faueri.
Genus name honors Magnus von Lagerstroem (1691-1759), Swedish botanist, Director of the Swedish East Indies Company and friend of Linnaeus.
Specific epithet means of the Indies in reference to native territory.
Common name is in reference to the crepe-papery inflorescences and the myrtle-like (Myrtus communis) features of the bark and foliage.
'Hopi' is one of several mildew resistant hybrids developed by the National Arboretum in Washington, D.C., all of which have been given Native American tribe names. It is a deciduous, upright, spreading, multi-stemmed shrub. 'Hopi' is a compact cultivar which features dark green foliage turning dull reddish-orange in fall, grayish-brown bark which exfoliates with age and terminal, crepe-papery, 6-7" long inflorescences (panicles) of light pink flowers from mid-summer to early fall. Flowers give way to round seed capsules which often persist well into winter. In the South, this cultivar can easily be grown as a woody shrub with a maximum size of 11' tall and 10' wide. In the St. Louis area where winter injury is a problem, plants will grow much smaller.
Problems
Two main disease problems of crape myrtles are fungal leaf spot and powdery mildew. Foliage may yellow (chlorosis) in alkaline soils. Some susceptibility to aphids and scale. Winter injury, particularly to top growth, often occurs in USDA Zones 5 and 6.
'Hopi' reportedly has excellent mildew resistance.
Uses
Good as a specimen shrub or in groups. Shrub borders or perennial borders. In the South where above ground winter hardiness is not a problem, this cultivar is also quite effective as a tall screen or informal hedge.