Auron,

Wisteria absolutely can be grown as bonsai (google image search "wisteria bonsai"). They are trained to show off the blooms. The rest of the year, they look terrible because they must be allowed to grow out and then be pruned successively. I'm still working out the pruning technique on my older Am. wisteria.

One difficulty is that when grown in a pot, they do not develop thick trunks. Specimen examples tend to be collected. not grown from seed or cuttings. They like being a bit rootbound in a taller pot (not a typical shallow bonsai pot) and have lots of water when growing (wet feet is OK).

Thanks tinyfrogs,

I won't be keeping it very small, I will probably have it grow to about 3' tall. I'm pretty sure mine is a wisteria floribunda (Japanese wisteria?). I figured it would not grow a large trunk in a pot, even it is a large pot. I just worry if I put it in the ground, when I want to take it out I will not be able too because of the aggressive roots....perhaps I should just put it in the ground far away from anything it can damage and shape it on a larger scale, like longwood gardens do with their wisteria.

Put it in the ground somewhere where it can't climb anything and where its roots won't mix up with plants you care about, like in the middle of a lawn somewhere. Train it for a few years to grow up rather than along the ground. Perhaps the lack of support might help it to develop a thicker trunk sooner, but also training it to wind around itself will give it some significant character. Digging it up shouldn't be too hard, but then I'm used to digging out big old bushes. Around here, collecting old wisteria is "common" (Triangle Bonsai Society has a newsletter online about it).

There were several Wisteria bonsai at the Sacramento bonsai show last April.
I took a few pics, although the lighting was sub-optimal in the building.

Here's another one with a thicker trunk. Poor quality picture.

Such beautiful bonsai! Sadly mine is not a repeat bloomer, or so I think. Pretty sure floribunda's are the one time a year large blooms. I'll just stick it in the ground somewhere and force it to go up. without giving it any actual support...assuming that will help thicken the trunk.