Sedum is a very large genus of almost 500 species in the stonecrop family, Crassulaceae. They are native to the Northern Hemisphere, extending further south in some regions. Plants in this genus are extremely variable, with alternate, opposite or whorled leaves. Most are succulent annuals, others being evergreen or deciduous perennials and shrubs, some of which are now included in the Hylotelephium genus. Many Sedum plants are cultivated for their attractive succulent foliage which comes in a variety of colours and forms, and for their dainty star-shaped flowers. They thrive in rock garden settings, can provide useful groundcover and are now used extensively in green roof planting for their tough, drought-tolerant qualities. Tender species are popular as houseplants. Sedum plants are toxic if ingested and can irritate the skin.