I bought a tiny Comfrey plant about 15 years ago, before I knew anything about Blocking 14. So mine seeds itself anywhere and everywhere. By the time you can see a new plant and pull it out, it's already established and comes back all the time and every year there are more and more - I may just disappear one day. I love the plant and use it a lot, but there are limits and I wish I'd known about Blocking 14 because once you've got the other sort, you've got it for life! But the bees do really love it.