Rhubarb root usually refers to the dried root of medicinal rhubarb species such as Rheum palmatum, a large perennial in the Polygonaceae family native to parts of Asia. The plant produces bold leaves and thick underground roots, and the dried root is the part traditionally used in herbal preparations.
This is not the same as casually eating pie rhubarb stalks from the garden. In herbal history, rhubarb root was valued as a strong bitter root and was prepared in measured amounts, most often as part of decoctions and traditional formulas.
