I've had comfrey for years and it is invasive here is we aren't careful. I have to admit I don't use it much except in a salve or oil I make for sores each year. I use equal parts torn up large leaf plantain and comfrey in hot olive oil. Allow to cool, remove leaves and drain them off into the oil well. If you want salve, reheat the oil and add some beeswax.
I think comfrey is a beautiful plant. I need to get some of mine moved into a more prominent place. It was in a raised bed that Holly removed for me last summer.
