Our comfrey was transplanted from 'The Patch' when we gave it up last year.
It's below a north-facing wall, and gets hardly any real sunshine, but has stormed away in its first year!
One thing which might have helped, is that it is directly over the drain to the soakaway from the septic tank, so it does two things - takes all the effluent, and grows huge plants and delightful flowers in the process!