Cool, thanks Phil.
I've heard of something called a "comfrey tractor" where you use something like an old milk crate, put dirt in it, grow comfrey in it, wait until the roots grow down through the bottom of the crate, into the soil, then you just give the whole crate a sharp twist to cut off the roots in the ground and move the whole thing to a new location where it will grow roots back down into the soil again and repeat. I've been wanting to try doing this myself.
it is easy to harvest root and make many plants