Any herb of the Eurasian genus Symphytum ( borage family).
Best known is the medicinal common comfrey ( S. officinale ), used to treat wounds and as a source of a gum used to treat wool. Traditionally it was also taken internally for various complaints. Organic farmers use it to deter slugs and as a green manure . The coiled sprays of bell-like, hanging comfrey blooms are usually pollinated by bees. Common comfrey is about 3 ft (90 cm) tall, with winged, hairy stems and blue, purplish, or yellow flowers.