They grow for me in southwest Georgia in sandy loam, near the Florida line. They're not the happiest little plants I ever saw, but they survive. I'm pretty sure they would grow better farther north, but I've kept them going for 3-4 years now. I've even rooted little pieces, which seem to fare better than the older plants. They want really good drainage and some lime.
They bloom once, early spring and deadheading does not make them keep blooming once it really gets warm.

Nell

They're doing well for me here in NE FL but I do have them where they get some afternoon shade.
Theresa