Joined: May 24, 2010
Location: Wellington, New Zealand. Temperate, coastal, sandy, windy,
Hi John, we don't have 'true comfrey' (Symphytum officinalis) in NZ, but the Bocking hybrids (Symphytum x uplandicum) are common.
Since Bocking's sterile but easily propagates from root cuttings, I'd probably go for that so I could control spread. It's a moot point really, since Symphytum officinalis isn't available to me.
Another thing in Russian comfrey's favour is it's extremely productive in terms of biomass: I can harvest mine at least 3 times a season.
I think Bocking 4 is supposed to be the most nutrient-dense, but Bocking 14's readily available here.