Rhubarb is a group of plants that belong to the genus Rheum in the family Polygonaceae. They are herbaceous perennial plants growing from short, thick rhizomes. They have large leaves that are somewhat triangular-shaped with long fleshy petioles. They have small flowers grouped in large compound leafy greenish-white to rose-red inflorescences. Although the leaves are toxic, various parts of the plants have culinary and medicinal uses. Fresh raw stalks are crisp (similar to celery) with a strong tart taste; most commonly the plant's stalks are cooked and used in pies and other foods for their tart flavour. A number of varieties have been domesticated for human consumption, most of which are recognised as Rheum x hybridum by the Royal Horticultural Society.