posted 13 years ago
Welcome to permies David,
Over here, we only have sterile Bocking cultivars; I won't get into the others, except to say I can't imagine comfrey that spreads by seed...
Comfrey is marvelous stuff, and I see it as being a vital part of my environment: the leaves are really high in protein, nitrogen, potassium.
The rules are (generally) that you only get out what you put in, and there's not all that many plants that love fresh manure, but in my experience comfrey and rhubarb can't get enough shit.
My biggest warming about comfrey is plant it where it can stay forever as it grows from every piece of root, and will also 'take' if the leaves are cut too low.
I see comfrey as a great permanentmulch plant, part of a fava bean, buckwheat, borage, whatever combo
but as far as nitrogen's conerned, I wouldn't think of it as my main source.
I don't have lawn, and I get the lawn guys to drop clippings. That is a lot of nitrogen!