For Lagerstroemia archeriana: Well composted soil with good drainage; full sun or a little shade recommended. Water sparingly and infrequently, allowing soil to nearly dry between waterings.
Just be patient. It will start itself. Both the crepe myrtle (blooming variety) and the wax myrtle (non blooming variety) will send out sister roots and these will become new plants about 2-5 feet...
Prune Crepe Myrtle in late fall. It's a southern plant and u want to wait long enough that it won't be hot enough to regrow. I say November or December. Also Crepe Myrtles are stripped of all limbs...
[1] A general garden fertilizer works well for crape myrtle. [2] Apply 1 tsp/5 ml monthly, March-August, along the planting hole edges of newly planted crape myrtles. Once established, 1-1/2-2 years...