I sent an e-mail to a friend on Roan Mt yesterday morning and she's not only got some tincture of comfrey that she bought, she has plants that she's going to give us so we can plant them.
There must be some low places for the comfrey to grow in there. It isn't really a high elevation plant, likes to keep its feet wet. It also needs very rich, deep soil. So maybe a raised bed isn't the best idea for it. What I would do is get some of that metal lawn edging and drive it into the ground around the plants. Otherwise they will be ALL OVER your garden as soon as you turn your back.
I haven’t been up to Roan for the blooms yet. Want to take a drive up Saturday or Sunday? ... I’ll drive, we can meet up with the lady and get the Comfrey for Mrs Don-o. I can use my new digital camera to get a few pix of the Rhodos, too.