Rhubarb is a vegetable derived from cultivated plants in the genus Rheum in the family Polygonaceae. The whole plant – a herbaceous perennial growing from short, thick rhizomes – is also called rhubarb. Historically, different plants have been called “rhubarb” in English. The fleshy, edible stalks (petioles) of other species and hybrids (culinary rhubarb) were cooked and used for food. The large, triangular leaves contain high levels of oxalic acid and anthrone glycosides, making them inedible. The small flowers are grouped in large compound leafy greenish-white to rose-red inflorescences.