I'm curious if cutting them back will diminish their ability to survive winter. I believe zone 6 where I live is typically listed as their hardiness limit. How do you manicure yours? At what time of year?
I have 4 clumps of them, and went ahead and cut one back as an experiment. The leaves are partially brown and limp, except close to the crown, where they're still green and turgid. They look really nasty right now, and I'd prefer to whack them way back, but not if it means risking losing them.
