Fertilizer and Watering
What is the frequency of watering and fertilizing crape myrtles here in San Antonio, Texas?
Certified GKH Gardening Expert
They generally do not need fertilizer, but it will not hurt to give it some if you want. If you do fertilize, use a balanced fertilizer (10-10-10). Generally, trees need at least 2-3 inches of water weekly (including rainfall), so I would water one or two times a week for at least 15-20 minutes (longer if it has been very hot and dry). If your tree is newly planted, this article will help: https://www.gardeningknowhow.com/ornamental/trees/tgen/watering-newly-planted-tree.htm
Other than making sure it receives plenty of water, you may want to add a good layer of mulch to help retain moisture and moderate soil temps, especially during hot, dry spells.