Wildlife Spotting

The reason I say this is that the chinese variety is a vast and fast spreader, which looks like what you have going on here. While almost all wisteria can spread via suckering (rooting of stray vines as they grown along the ground) the Chinese variety is the most prolific of these. Also the Japanese variety produces much larger and longer flower tendrils, they tend to reach upward of a meter, while the Chinese variety tend to be not as lengthy and more compact, although just as fragrant. :-) To keep them from spreading, you need to start at the main plant, trim off the trailing vines growing along the ground, and gather the main body of vines into a confined grouping, (using twine and a stake) and wrap them around each other to form a sort of trunk, this way the vines will be forced to grow up and out instead of just out.

I am almost inclined to say this is the chinese variety. Wisteria sinensis.