Here's my anecdote. I put four rhizomes (2 Columbus/2 Chinook) in three years ago that I bought from a commercial place out in Washington State. Getting great harvests, btw. This spring, I pulled up some of the landscaping fabric I used to keep the weeds down around the plants (with mulch on top) and found about 50 feet of runners that were ready and willing to root. I cut out a few 4-5 inch lengths and planted them in the soil (early April) its May 22 and each is over a foot tall looking for something to climb. Also, I gave about 20 feet of it away - and I'm told that has produced plants too. Anyway, my point is that I think it may be harder to kill these things than to propagate them. Go hops!