Sempervivum tectorum

Sempervivum tectorum, commonly known as the common houseleek, is a rosette-forming succulent evergreen perennial in the family Crassulaceae. It spreads by offsets and produces clusters of reddish-purple flowers on erect stems during the summer.

It is native to the mountains of southern Europe but has been widely cultivated and naturalized across the rest of the continent. It thrives in hot, dry environments and is traditionally grown on roofs and stone walls.

It is widely cultivated as an ornamental groundcover for hot, dry places and has received the Royal Horticultural Society's Award of Garden Merit. Historically, it was also intentionally planted on house roofs for protection.

In traditional herbal medicine, the plant's juice was used as an astringent and applied to treat skin conditions, eye diseases, and inflammation. It was also mixed with honey for oral thrush and used in historical external remedies for contusions.

The plant was widely believed to protect buildings from lightning strikes, thunderstorms, fire, and witchcraft. It was strongly associated with thunder deities, earning names linked to the Roman god Jupiter and the Norse god Thor.