Tony Avent has kept his going for at least seven years by setting them in a scree like embankment by the road. He is in USDA Zone 7, so you should succeed as long as they have drainage.

While visiting the late Kim Kuebel in Boerne, Texas in the late 80s, we visited one of the original sites. It was the flood plain of a creek in caliche soil. This is a high lime clay, nasty to work with.

Mine overwintered from last year but that wasn't a real test because this past winter was very mild It got taller than me! It did not bloom at all in 2005 but this year it start