Years ago I was doing a segment on KDKA-TV about native plants. The nursery sold me this purple lysimachia, it's not a native and it's extremely invasive. The first few years I loved the plant's purple foliage and yellow flowers, but then it took over.
It spreads by underground runners and I doubt I'll ever get rid of it. Today I'm headed out to garden to gently pull out as much as I can. Every piece of root I leave in there will become another plant.
There are a couple of other ways to deal with invasives. Continual top cutting is an effective way to battle them. Every week cut the tops of the plants, which eventually die because the foliage cannot provide nourishment for the roots.
The last-ditch effort is to cover the area with something that stops light from reaching the plant. That might mean landscape fabric or a tarp. Leave it on all season and you'll kill the plant.
I didn't know enough not to plant lysimachia then, but I certainly know better now.