It has been introduced(escaped from cultivation) into several states. Has been documented as far north as Ohio, Western NY and the Mtns of western VA. The Missouri Botanical Garden(MOBOT) rates it's cold hardiness as -10F(Zone 6)
It would not be an evergreen species for you, even here in Z7, they eventually die back each winter and emerge with a new flush of growth in late spring.
Nurseries usually offer the cultivar, 'Rochfordianum'. a larger and more showy plant, than the species.
For extra protection, you may want to cover them with conifer boughs for the first couple of winters, until they become well establihed.
Hope this helps.
Rb