Rheum is a genus of perennial plants that grow from thick short rhizomes. The genus is in the family Polygonaceae, and includes the vegetable rhubarb (Rheum rhabarbarum or Rheum x hybridum.) The plants have large leaves that are somewhat triangular shaped with long fleshy petioles. The flowers are small, greenish-white to rose-red, and borne in large compound leafy inflorescences. A number of varieties of rhubarb have been domesticated both as medicinal plants and for human consumption. As leaves are toxic, the plant's stems are used in pies and other foods for their tart flavor.