Comfreys are great plants to have in the garden. Bees love the flowers on all Symphytum species and they have the reputation for being "dynamic accumulators" i.e. especially effective in processing nutrients and minerals from the soil and releasing them back into the ground when the plant dies back.
 Symphytum orientale (pictured) is perhaps the most elegant with pure white flowers. I divided some clumps from my father's garden and planted them under the apple tree where they might be beneficial as a green manure.
 Elsewhere I've planted Symphytum Hidcote (white flowers tinged with blue or pink) and Symphytum grandiflorum aka Creeping Comfrey (white flowers with a creamy yellow tint). Both of these are lower growing and make good groundcover. Some books list comfrey among the weeds but it's way too good for that.