Rhubarb

Rhubarb is a herbaceous perennial plant in the genus Rheum and family Polygonaceae, grown from thick rhizomes for its fleshy, edible leaf stalks, or petioles, which are cooked and eaten though its large triangular leaves contain toxic oxalic acid. Though it is a vegetable, rhubarb is used culinarily as a fruit, most often sweetened with sugar and baked into pies and crumbles, and its stalks can also be eaten raw while still crisp. Culinary rhubarb likely arose in early eighteenth century England and Scandinavia through hybridization of two Asian species, and the Royal Horticultural Society now classifies modern garden rhubarb as Rheum x hybridum.