Comfrey is a perennial herb of the family Boraginaceae with a black, turnip-like root and large, hairy broad leaves that bears small bell-shaped white, cream, purple or pink flowers. It is native to Europe, growing in damp, grassy places.
Comfrey, also known as knitbone, has traditionally been used to treat wounds and reduce inflammation associated with sprains and broken bones. The roots and leaves of comfrey contain allantoin, a substance that promotes wound healing and tissue regeneration.
The proboscis (the tube for collecting nectar) of earth bumblebees is too short to reach the nectar in comfrey flowers. Hence, they bite holes into the base of comfrey blossoms. They then steal the nectar without pollinating the flowers. This interesting behavior explains why I had a hard time to find an inflorescence, which was not completely perforated.