comfrey?

I have been reading about the Bocking 14 cultivar of Russian Comfrey ( Symphytum x uplandicum), sounds like great stuff, I would love to grow some for making compost tea and to add to my compost,but it seems to be difficult to locate.. I found one place that sells root cuttings but it would cost me almost $20 including shipping, ouch! Anyone have any opinions about whether the benefits are worth the cost? does anyone use it or know of a cheaper source for root cuttings?

I use the standard comfrey, Symphytum officinale, since we also use the plant medicinally. The Russian Comfrey has a higher level of the problematic alkaloids.
The potatoes and the compost love the regular comfrey too.
Are you looking for the Bocking 14 cultivar to prevent seeds?

yes, I've heard that the seed bearing cultivars can become invasive.

Cut the flower stalks off before they set seed. Actually, it's the root that can be invasive if you don't get all of it. Comfrey will put down very deep, strong roots. They are a bit brittle, so if you try to just pull it out, the roots will break off, leaving a portion to sprout again. We use a lot, so I have not found it to be a problem. The bees love the blossoms.

I'm also interested in growing comfrey for improving compost. The cheapest supplier I could find for Bocking 14 (they also have Bocking 4) was Richter's.
By the way, can anyone tell me how far apart the plants need to be - I've read both 3 feet each way in squares, or two feet within the row and three feet between rows.

My experience with the standard comfrey is that it gets rather tall and wide. I'd say about 4' apart would be better.

4 feet apart is good for the standard one.

The comfrey I started from seed forms big leaves that compost nicely. Yes, they reseed with abandon, but they're easy to pull out. Another benefit is that bees just LOVE the beautiful blue blooms, and they need all the help they can get these days.

I've left the comfrey, mints, cabbages etc go to bloom after harvest because the bees love the blossoms so much. Some of our local master gardeners gave me a lot of flack about this until I pointed out how many bees, parasistic wasps and other beneficial insects could be see all over these blossoms. The herb garden serves double duty as the insectary. Many of these plants were the first blossoms in spring to offer food for the insects.

GM, I'm so curious - what was their reasoning?
I've done this for many years and after considering the situation, can't come up with anything negative.

The reasoning was that it didn't look "pretty", as in, not manicured, and the paranoia of the mints spreading. I've grown mints in the ground for decades and not had them take over the garden. When I harvest the mints, I pull the entire root back to the mint's designated space and clip it off below the soil surface. I'll trim trim all the roots back this way at least once a year, usually in the fall. They stay well behaved that way.
Nothing wrong with a mint in the ground. You just need to manage them. Lazy gardeners or irresonsible plant guardians can grow them in pots. LOL!