I've had to go dig and remove chunks as well, only so many friends who will take enough, or any..
Also cut off bloomed stems before any seeds can fall. But they spread by roots so well, it is hard to get it all.
I had found it wild, then got some cultivars in swap, so I have a couple colors, plus Sweet Kate with chartreuse leaves.
Maybe a good one to plant with competing tree roots to rein it in..