Anna, I think it might survive a Wisconsin winter in the ground with a really good mulch, but not in a pot. The pot's up in the air and would freeze hard for sure. It would also dry out, and if you watered it, you'd get freeze/thaw and heaving plus probably break the pot.
Maybe if you could sink the pot into the ground for the winter, and mulch it really well that might give it a better chance. But that might be both more risky and more trouble than pruning it and putting it in the greenhouse.
