"Pretty hardy stuff, wisteria. I have not, however, planted any from seed, so I dont know how that goes. With how tough they are in general, I would think a plant that has grown for a full spring/summer/fall should be fine outdoors in the winter. I swear my landscape tree grows an inch per day ;0) "
Wisteria is very hardy, but to varying degrees. It slows growth dramatically the further north it is in the U.S. The explosive rampant growth we get here in the middle Atlantic states isn't the same as what happens in upstate New York or Wisconsin...Also, a stiff frost in April when containerized wisteria are pushing blossoms will kill the flowers. I have friends with a huge collected containerized wisteria (10 inch trunk, cascade) that is moved into a greenhouse on April nights when frosts are expected. They left it out once one April night just before a show and it dipped to 30 F. It was loaded with flower buds just ready to open. It dropped every single one two days later...