Now that's a dog! Beautiful!
The purpurea can be troublesome if you don't cut them back before too many seeds develop. I just keep pulling the seedlings out. I like them so let them cross and find something new each year.
The Nils are a different story, you may want to try them, and there are so many different colors. They very rarely over seed in winter and if they do it is only a few. I have tons of both the purps and nils if you want to try some. They do well in pots too so you can keep a handle of the seeds.
