On a normal winter, we have only a few days of snow cover, and constant freeze/thaw cycles. My penstemons not only thrive, but self-seed everywhere! Husker Red is 3' tall now, blooming like crazy, and it is 100 yards away from where I planted the first one 3 years ago. (Winter of 2010, temps got down to 17 below, so i know these are very hardy. We had no snow cover when we had the extreme low temps.)
I think they are crossing, too, because I have some newer shades of purple and pink that came out of the Pikes Peak purple .
