search the forum- there was a thread this spring about amethyst falls. i ripped out some of the chinese stuff myself last yr after seeing the light as to how invasive it is. mine hadn't bloomed either, and had been in the ground several yrs. from what i've read, that isn't unusual for seed grown wisteria. i bought an am falls last yr, couldn't decide where i wanted it, and it bloomed in the pot again this spring- in the shade even.

Wisteria frutescens is a very good plant in my opinion. It is not nearly as rampant as the exotic species, and blooms late enough to avoid frost damage. The fragrance of Amethyst Falls is, at the least, kind of musty. To me its very similar to some Camellia sasanquas. A 20' by 20' spot in sun sounds really good to me. One that size in full flower would be stunning! It may grow a little bigger but is easy to keep in place. I've had an 'Amethyst Falls' since June 1997 and it has been wonderful. Heres a picture from May 10, 2005........

With wisteria being considered a hardy vine...even with the noninvasive one...I would imagine it wouldn't kill itself out. I have a trained tree form I am planning on propagating. I believe the one site I went to said 3-4 foot spacing is the rule. So...I feel you should be fine.

The roots aren’t as much of an issue to my mind as planning to grow the vine on your home. Even the American ones can get to be large, heavy vines, and can do things like peel up shingles in looking for something to grab. It really is better on a heavy duty pergola or similar IMO.