Symphytum uplandicum, Russian Comfrey, is a perennial herb native to Europe. It comes from the Forget-Me-Not family of plants, and is perhaps one of the most well known and recognized medicinal herbs. Russian Comfrey is a fast-growing, hairy leafed and herbaceous  with small, gorgeous bell shaped rose-to-purple flowers. Russian Comfrey has a large, black turnip like root which is often used for medicinal purposes. 
Because Comfrey roots penetrate deep into the soil, it accumulates large amounts of nutrients. At the end of the season, grind up your unused plants including the root, and mix into your soil to help provide needed nutrients.