Growing Eucalyptus in Colder Climates (Zone 6)

From what I've read, most cold hardy eucalyptus are only rated up to about Zone 8. I would like to plant some Blue Gum eucalyptus trees and zone 6 in the Appalachian Mountains. Where I live it is very cold in the winter, and definitely freezes, for days at a time. One thing I read is that the trees will turn into a annual tree instead of a Evergreen tree if they are in a colder climate, what I don't know is how much of the tree itself will actually die. In the spring will the new growth Come From the Bottom, as a new tree, or will the tree pick up where it left off? Also the particular variety I like, the Blue Gum, aren't the most cold-hardy ones. By here in the Peruvian Andes (returning to Maryland next week) they grow quite well, though frosting is rare here even if it is very cold at night.