Sedum is a large genus of the Crassulaceae, representing about 400 species of leaf succulents, found throughout the northern hemisphere, varying from annual groundcovers to shrubs. The plants have water-storing leaves and a typical form of blossom with five petals, seldom four or six. There are typically twice as many stamens as petals. Well known European Sedums are Sedum acre, Sedum album, Sedum telephium, Sedum dasyphyllum, Sedum rupestre (also known as Sedum reflexum) and Sedum hispanicum.
Sedum acre or "biting stonecrop", has a sharp, peppery taste and contains poisonous alkaloids (piperidine). Depending on the amount consumed, irritations of the mucous membranes, cramps and paralysis, including respiratory paralysis may ensue. In ancient Greece, biting stonecrop was used to treat epilepsy and skin diseases, as well as to cause abortions. Sedum reflexum, known as stone orpine or crooked yellow stonecrop, has a bitter and sour taste, and is occasionally used as a salad leaf or herb. Sedum telephium is also used in this manner, but even more rarely.
Many sedums are extensively cultivated as garden plants, due to their interesting and attractive appearance and hardiness. The various species differ in their requirements; some are cold-hardy but do not tolerate heat, some require heat but do not tolerate cold. They are preferred to grass for green roofs, popular in Germany and some other countries. Sedum species are used as food plants by the larvae of some Lepidoptera species including Grey Chi. In particular, Sedum spathifolium is the host plant of the endangered species, San Bruno elfin butterfly of San Mateo County, California.