At 12:12 PM 4/25/2007, you wrote: >P. caerulea is not just hardy here but somewhat invasive. I don't >grow it but my brother does, and new plants come up a metre or more >from where the original plant was put, so I assume it is rhizomatous. That sounds like P. incarnata, too. I grow it at the base of some trees and it pops up all around in the lawn. Dennis in Cincy