I planted a Crepe Myrtle in June. I thought I watered it enough, but apparently not. The tree started losing its leaves, but I did have some blossoms on the lower part of the tree. I started providing more water and noticed some new leaves, again on the lower 3/4 of the free. The top of the tree was loaded with buds, which never bloomed. Now the majority looks like they are dying. We had an extremely hot, dry summer; however, we've had some good rain in the past week.
Remaining Buds Are Dying, Never Opened
Certified GKH Gardening Expert
Lack of water would shut down the production of flowers and leaves.
The plant sends it's energy to the roots to protect itself.
Here are some links to refresh you on the care requirements.