Answer: Comfrey (Symphytum officinale) and Borage (Borago officinalis) are members of the same family (Boraginaceae). Comfrey (Russian or common) has a reputation for improving soil, but Borage doesn't receive the same enthusiasm, probably because it readily self-sows and can become invasive. The properties of either/both plants should be similar, making them desireable green manure crops. If you grow either, turn the plants under before they flower and set seed.
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