Answer: If it perks up when you water it, there's something going on with the root system and I think it would be worth the effort to dig it up and make sure the planting site and root system are healthy. Even with lots of water, if it's planted in a sandy site, moisture will drain away quickly and the tree may not get enough water. Dig the tree, and amend the planting area (not just the planting hole) with organic matter to facilitate good drainage yet hold an adequate amount of water. When you replant, place a cone of soil at the bottom of the hole and drape the roots over it in a natural fashion. Then backfill, gently tamping the earth down. Water well to help settle the soil. This should give the roots ample room to grow and promote a deep root system which will be better prepared for summer heat and drought.
Best wishes with your crape myrtle!
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