How deep are the roots of a wisteria plant?

Here is some information that might help you - https://www.gardeningknowhow.com/ornamental/vines/wisteria/wisteria-root-system.htm

They get quite extensive so it depends on the age and size of your plant. When I was a child my father cut down and killed my mother's wisteria...because the roots were siphoning so much water from their acre of vegetable garden.

They are a pain to get rid of. Just keep pulling and cutting until they Die off!!

They aren't deep, they spread out a lot. If you have a southern exposure, they will do well. Mine actually bloomed twice a year because they had protection from too much wind & sun. Usually they only bloom once.