They spread from underground rhizomes so have a complex and widespreading root system. You can dig them up - I've done that myself - but that seldom provides complete control immediately. Takes a couple of attempts. Or you can do the herbicide route (painting on cut stems) but that may also require multiple applications.

That is a very small area. Dig up what you can see and spray anything that resprouts with round up. Shouldn't take much work at all.

We have it throughout both giant beds in our backyard. We have pulled and pulled and dug it up, but it keeps coming back.