gardenlady:
1st you should dig some of the runners (with tuber attached)pot it and keep in a warmer location to insure you still have a plant next year. For the plant left outside don't cut it back pile leaves or mulch up on and around your plant. I would use mulch personally so some of the heat generated from the decomposition process will help keep it warmer.As I recall you get to cold for you plant to winter over.
I will let someone that has done this before give you specifics. I would think if you could grow your plant
on the south side of your home (right up against the
foundation).That it would have a better chance of success
as the earth should be able to absorb some heat from your home. You may have to get inventive and try some other overwintering processes.
Art
Art