The Right Place
While it is not completely safe to plant a crape myrtle north of Baltimore, MD, new, hardier hybrid crape myrtle varieties are available that can handle winters where temperatures occasionally fall to 0F (zone 7). Planted in protected places, crape myrtles will survive in areas in the East Coast somewhat farther north (zone 6). However, they do not like the actual seashore because of the humidity and fog. Sometimes above the Mason-Dixon Line they fall victim to frost and die back, but their roots are hardy and will generate new growth in the spring. Under these conditions crape myrtles stay small and can be treated like any perennial plant. They make excellent plants for the South and West Coast also, being hardy in those climates.
Planting Nursery Stock
Crape myrtles like full sun and, ideally, moist fertile soil, either loam or clay. The more organic matter in it such as peat moss, compost or decayed sawdust, the better. They prefer the soil to be on the acid side (pH 5.0 to 6.5). Choose nursery stock that is in a container or has its roots and soil ball wrapped in burlap. Bare root shrubs are difficult to transplant. The best time to transplant is late spring or early summer when the young plant is actively growing.
Keep the shrub moist until planting time. Remove the container or burlap wrappings, taking care to keep the soil ball intact. Gently spread any matted, tangled roots that protrude from the soil ball, clipping those that might be coiled from an overlong stay in the container. Dig a hole wide enough to accommodate the soil ball and just as deep as it is. Set the shrub in the hole, taking care that the surface of the soil ball is even with or slightly above ground level. Fill the hole with soil, gently firming it over the root ball and water generously. Do not fertilize at this time. For hedges, space young shrubs 4 or 5 feet apart.
For more information see file on Planting Shrubs.