Lagerstroemia indica 'Whit I'

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 buddlejas) by cutting all stems back to 8\ in early spring each year. Roots will sprout new stems which typically will grow 2-5' tall by the end of the growing season. Flowers will appear on the new growth. It is an option in St. Louis to grow this plant as a woody shrub by pruning it back to live wood in spring at the time the new foliage appears (in somewhat the same manner as with a shrub rose). With protection, top growth will survive some winters, but will still suffer significant injury or die to the ground in harsh winters."