It seems that the growing zone is all over the charts, and depends on what site you are looking at. Some say zone 3, others zone 7.
It has been down to single digits in my yard with full exposure to ice, very little snow, and lots of rain through the winter and spring. It does need fast draining soil, lack of it seems to be the real killer of this plant.
Let us know how yours does through the next winter season. That should give us a better idea of what it is capable of.
