I have a non-native bamboo. It’s in a marshy area. It is soft light green. It dries to wood every year. And I cut it like firewood and chip it. Then suddenly it grew back and is growing to an acre size. It even flowers: soft light white vanilla flowers for the bees. Can I rototill it under and seed in native Northwest groundcovers?
It is difficult to do plant identification by description alone, but it sounds like you may have Japanese Knotweed (Polygonum cuspidatum)
It is extremely (!) hard to control this plant. Rototilling it will make hundreds of new plants because it grows from the tiniest root fragment, so do not do that!
There is a lot of good information on it on the Internet, but here are two good links:
King County, which lists it as a Class B noxious weed (control recommended but not required by law)