The message
from "pronoun" contains these words:

I recently bought Russian Comfrey (said to be non invasive) from Barwinock
Herbs. Online, but I don't have the address.

It's propagated from root cuttings. So it's not a good idea to
rotovate even the sterile, non-creeping kinds of comfrey into the soil
unless you're planning a really large plantation of it ;-)

Janet.