Personally I don't care if they become a weed here. If you could only see our fields... they are full of weeds already. I would rather see a field of sunflower type flowers than what's there currently. Plus the seed heads will be bird food.
I found a supplier in New Brunswick and will be ordering 1 lb of tubers in May. They charge $8.50 for 1 pound of tubers. And $11 a pound for the red types.
Mapple Farm
129 Beech Hill Rd.
Weldon NB Canada E4H 4N5
wingate@nbnet.nb.ca
They will email you a text copy of their catalog. They have lots of interesting stuff there!