Symphytum officinale is a perennial plant native to Europe and Asia. They are commonly called comfrey or knitbone. This plant has a long history of cultivation as a medicinal plant; it was a famous remedy for broken bones in the Middle Ages. The young leaves were eaten as a vegetable, and the dried roots were used along with dandelion roots as a coffee substitute. Nowadays, the whole plant is mulched down and used as a rich source of green manure by gardeners. The rich mucilage contained in the plant makes this a useful medicinal plant. Historically, the roots and the leaves were used for wound healing, both external and internal ulcers. Recently, research has shown potentially dangerous levels of pyrrolizine alkaloids, mainly in the root, and the plant is now only recommended for external use. Externally, herbalists use comfrey leaf and root to treat broken skin. The traditional uses on wound and muscle pain have been confirmed.