Sempervivum tectorum

Sempervivum tectorum, the common houseleek, is a species of flowering plant in the family Crassulaceae, native to the mountains of southern Europe, cultivated in the whole of Europe for its appearance and a Roman-era tradition claiming that it protects buildings against lightning strikes.

Description

Growing to 15 cm (6 in) tall by 50 cm (20 in) broad, it is a rosette-forming succulent evergreen perennial, spreading by offsets. It has grey-green, tufted, sessile leaves, 4–10 cm (2–4 in) in diameter, which are often suffused with rose-red. In summer it bears clusters of reddish-purple flowers, in multiples of 8–16, on hairy erect flat-topped stems. The species is highly variable, in part because hundreds of cultivars have been propagated, sold, and traded for nearly 200 years.

Sempervivum tectorum was described in 1753 by Linnaeus, who noted that its leaves are ciliate, that is, fringed with hairs.