what is the main difference between red russian comfrey and the seeded variety of comfrey?

I found the seeded variety at horizon herbs and I was wondering if it is something I would want to grow.I have the russian variety already.Would it be ok to nix the two?I'm using it for earthworm food and livestock food and composting.

They're pretty much all 'Russian' comfrey. That was the name given to them when first imported into England. The Bocking varieties are hybrids, developed half a century later, and do not produce viable seed.

The 'True comfrey' (the one that produces viable seed) is the one most preferred for medicinal purposes. The Bocking varieties are the ones preferred for fodder and biomass. They have been bred for those traits.

So, it depends on your goal(s). If you want to grow it for medicine, the seeded variety would probably be your first choice. However, if your goals are for fodder, and compost. then one of the Bockings should be first choice.