any of numerous low-growing succulent plants constituting the genus Sempervivum, about 40 species, in the stonecrop family (Crassulaceae), native to Europe, Morocco, and western Asia. The name houseleek refers to the growth of some species on thatched roofs in Europe; “live-forever” indicates their hardiness and durability. Houseleeks usually have thick fleshy leaves arranged in a dense rosette. Small plantlets, or offsets, arise in a cluster around the parent plant. They are useful in garden borders and rock gardens and are attractive in window pots indoors.

The common houseleek, also known as old-man-and-woman or hen-and-chickens (S. tectorum), has given rise to a number of cultivated varieties of horticultural interest. Cobweb houseleek (S. arachnoideum), with leaftips connected by weblike strands, has also yielded many desirable varieties.