You have to know the variety. Crepe myrtles basically come in the L. indica or L. fauriei flavors. There are a few L. indica x fauriei crosses out there, too.
Muskogee is a pretty well known cross. Biloxi is a cross, too, I believe. Appalachee is a fauriei.
The extra tall ones are generally faurieis.
I don't know where they can be ordered, though. I have collected mine from various places and people. There is a nursery in Tennessee Colony, TX that sold us many hundreds of them for our local master gardeners plant sale last year, and I had quite a few left over from that.
In fact, the Biloxi pictured above came from them.
