I've had great success propagating comfrey by digging up a root, cutting it into 2 cm pieces, taking a piece of 12mm rebar and jamming it into the group then dropping the root pieces into the resulting hole.
However, now that we have 10 acres, I need something more generous. There are large areas of terrace banking that need stabilising for example and doing the job at 2cm a timne is not going to cut it.
I've been thinking about taking the root, tossing it through the mulcher to get many many small pieces, adding it to some compost, mixing well and applying to the desired area. The question is, how small a piece of comfrey root can I get away with?
Any ideas? Better still, any experience?