Hot weather doesn't faze crape myrtle.
When watching the Olympics over the weekend, I was interested to see crape myrtle shrubs lining a portion of the route of the women’s marathon. I’d heard all the talk about Beijing’s typical high summer temperatures, and this brought it home to me – crape myrtle ( loves hot weather.
That’s one of a trio of main requirements for successfully growing them. The second is planting in a location with full sun. Not sun part of the day or partial sun all day, but all sun all the time. Otherwise, it won’t bloom well.
The third crape myrtle necessity is also temperature-related: winter temperatures no lower than zero degrees F. (and higher is better). That means living in Zone 6b and higher. Zone 7 is more reliable. (Hopi is the variety that's often considered the most cold-tolerant.)
Well, I guess there’s a fourth thing to think about when choosing and planting a crape myrtle – space. These aren’t tiny plants. Although there are a handful of “dwarfs” – which grow less than five feet tall – most crape myrtles end up in the 10- to 30-foot range, and some can climb to more than 35 feet high over a period of years.
When I lived in the South, I saw some of those really big ones as wide as they were tall and covered with blooms. Wow!
But as impressive as they were, the older varieties of crape myrtle had some problems: They weren’t cold-tolerant, they mildewed easily, and leaves sometimes became covered with black spots. Most also grew too large for ordinary yards.
Those drawbacks are mostly a thing of the past, thanks to breeding done by Dr. Don Egolf at the National Arboretum, who pretty much revolutionized crape myrtles. He released about 30 cultivars that have greater cold-resistance, are mostly tolerant of mildew, and grow to varying sizes.