Canadian Gardening: Question about Cannas, 1 by OldFlowerGirl

OldFlowerGirl wrote:
I have a question I hope some of you might have an anwer for. I have a 3 Cannas that originated from a single plant that my daughter gave me in May of 2003. The first year I planted it in the ground and it did wonderfully, grew to be 5 ft tall or so, but no blooms. I cut it down in the late fall and dug up the rhizomes and stored in the basement for the winter. This year, I divided the rhizomes and had enough for 3 plants. I planted 1 in the ground again and two in large pots. Again they did extremely well, growing tall and healthy with enormous green leaves. Still no blooms. Now I was reading on another forum, a group of Americans discussing their Cannas. There I learned that they won't bloom until after they have matured and have been planted for a year or two. So how do I get my Cannas to bloom if I have to keep digging them up every fall after only about 5 months? Have any of you had luck leaving them in the ground over winter? They gardeners I was lsitening to were in Zones of 7 and up. I am in a Zone 5b. I think leaving them in the pots in the winter might have them quite root bound by spring. What does everyone else do with their Cannas...please?