On Apr 26, 9:46*am, "Eric" wrote:
I have a large perennial garden here in zone 5. *I am losing many plants per
year over the winter and all varieties are well suited to zone 5. *Most of
the divisions I made from larger plants were lost over the winter and these
were large healthy growing plants. *This past winter, the winter was mild
here in southern New York and I still lost a lot of plants. *Any ideas?

Probably the most significant issue in pushing the growing zone for
perennials is good drainage, wet things don't winter well.