Iris cretensis is cold hardy for me in SW Ohio. I used to keep it potted & indoors in winter, but at the advice of iris guru Bill Shearer I've had it planted in the ground for about 16 years now in flower beds near the house. I've had it bloom on Christmas Day, New Years Day, and just about any other day in winter that happened to be warm & sunny. The main flush of bloom is always in February/March though. Dennis in Cincinnati