Best grown in average, medium moisture, well-drained soil 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, however. Water roots deeply, particularly in dry spells, but avoid wetting the foliage. Plant in a protected location and apply a good 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 5b to 6a), it is perhaps best to grow these plants as perennials (like buddleias) by cutting all stems back to 8" in early spring each year. Roots will sprout new stems which typically grow 2-4' tall 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 shrub roses). With protection, top growth will survive some winters, but will still suffer significant injury or die to the ground in harsh winters.
This crape myrtle cultivar (a cross between L. indica and L. fauriei) 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.
The two main disease problems of crape myrtles are fungal leaf spot and powdery mildew. This cultivar reportedly has excellent mildew resistance. 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.
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.