Re: removal of bishops weed
I fought a long running battle with this "weed" at our previous property. I tried repeated applications of round-up - 3 applications - which did not work. Digging, as you would weeding, did not work. I discovered that every single piece of rhizome with a viable node will produce a new plant. Digging just resulted in hundreds of new plants that continue to pop up over the next 1-2 months - impossible to deal with, especially on a perennial bed.
What won the battle for me was digging every square inch of soil, sifting it with a 1/2 sift to remove every single piece of rhizome. Victory was earned, bed by bed, square yard by square yard. I had to do this fast enough - before rhizomes have started to invaded from the surrounding "untreated" areas.
Other people must have their own tale to tell about this invasive plant. I still see it offered in the big box stores and the nurseries. I cringe when I see that. It should come with a warning "If you grow this plant in your garden, be prepared to put up with it forever."