We are going to build a pergola this summer. I love trumpet vines on pergolas. Since I live on the Wisconsin/Illinois state line, ( supposedly zone 4b/5a) would a trumpet vine be hardy if I planted it in a large (20 inch, at least) pot and left said pot outside during the winter? I do have a greenhouse, so I could prune the beast back hard and put it in for the winter, or do they need a cold/dormant time? I really don't want to plant one in the ground because I know they can overtake an area in a short time. (think "The Trouble With Tribbles..........") LOLOL

I think the root systems are pretty big. I know the roots like to spread.

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.

I can prune and put in the g'house. That is not a problem. I will have to discuss it with the SU, maybe he won't care if it grows all over creation. LOL Just wanted to know my options.

I'd be surprised if trumpet vine failed survive the winter in a pot, even in Wisconsin. It's nearly indestructible in our climate, which is pretty similar to yours except ours is somewhat drier. The biggest problem will probably be the roots expanding to the point where they break the pot. You might need to dump it out of the pot each spring and severely root prune it, much as you'll have to do with the top growth.