RE: Crepe Myrtle for the Summer Heat.
Crape myrtles are wildly popular in the South for good reason. They bloom in the summer, when there are few other trees and shrubs providing that service. The larger varieties grow rather quickly, providing a bit of shade in addition to the seasonal color.
All crape myrtles are sun lovers, generally cold hardy in zones 7-10, although there are some that will work in zone 6 as well. They are extremely heat-tolerant and quite drought-tolerant once established. Plant them in full sun, amending the soil with soil conditioner to provide a moist and well drained situation.
Care is minimal for crape myrtles. Fertilize in spring with a general purpose shrub fertilizer—cottonseed meal works great—and keep it mulched to maintain consistent soil moisture and temperature. Water periodically during dry spells.
The major problems with crape myrtle include Japanese beetle, aphids, whitefly and powdery mildew. Again, providing a good location and proper sizing to fit the site will minimize most of these problems, but monitor for them and treat as needed.
Crape myrtles, like most other commercially available plants, come in a wide selection of varieties. Not only do they differ in bloom color and cold hardiness, but also in mature size, bloom time and disease/insect resistance.