Rheum is a genus of about 60 perennial plants in the family Polygonaceae. The genus includes the vegetable rhubarb (Rheum rhabarbarum or Rheum x hybridum.) The species have large somewhat triangular shaped leaves with long, fleshy petioles. The flowers are small, greenish-white to rose-red, and grouped in large compound leafy inflorescences. A number of varieties of rhubarb have been domesticated both as medicinal plants and for human consumption. While the leaves are toxic, the stalks are used in pies and other foods for their tart flavor.
Rheum rhabarbarum, Rhubarb is a species of plant in the family Polygonaceae. They are herbaceous perennials growing from short, thick rhizomes. They have large leaves that are somewhat triangular, with long fleshy petioles. They have small flowers grouped in large compound leafy greenish-white to rose-red inflorescences.
In culinary use, fresh raw petioles (leaf stalks) are crisp (similar to celery) with a strong, tart taste. Most commonly, the plant's leaf stalks are cooked with sugar and used in pies and other desserts. A number of varieties have been domesticated for human consumption, most of which are recognised as Rheum x hybridum by the Royal Horticultural Society.
Rhubarb is usually considered to be a vegetable; however, in the United States, a New York court decided in 1947 that since it was used in the United States as a fruit, it was to be counted as a fruit for the purposes of regulations and duties. A side effect was a reduction on imported rhubarb tariffs, as tariffs were higher for vegetables than fruits.
Rhubarb also contains glycosides especially rhein, glucorhein and emodin which impart cathartic and laxative activities to it. It is hence useful as a cathartic in case of constipation.