There are different kinds of Confrey. The kind I have I would not wish upon my worst enemy. I started with 1 purchased plant. It is recommended for feeding to animals to keep them healthy.. I have long forgotten what it is good for. It spreads by seed, and by underground roots.At first I thought "Yay, free plants!" The roots grow to the size of baseball bats. In my sandy soil they are growing straight down beyond the total reach of a shovel. We though tiling it up would be a great idea. Each bit of root turns into a new plant. We have dug out tens of thousands of plants in the last 20 or so years. We have it under control but, only by tenacious removal and never let it go. There are comfrey cultivars that are not so invasive. Research it before you get any..