Cobweb House-leek

The cobweb house-leek (Sempervivum arachnoideum) is a distinctive succulent plant in the family Crassulaceae, immediately recognizable by the dense network of white, cobweb-like hairs connecting the tips of its rosette leaves—an adaptation that may protect the plant from intense ultraviolet radiation, desiccation, and grazing at high altitudes. Native to the mountain ranges of Europe, including the Alps, Apennines, Carpathians, and Pyrenees, this species colonizes exposed rocky outcrops, cliff faces, scree slopes, and thin soils from subalpine to alpine elevations, often growing in large mats. The rosettes are small, typically 1–3 centimeters in diameter, composed of densely packed, fleshy leaves colored green with reddish or purplish tips. Like all sempervivums, S. arachnoideum is monocarpic at the rosette level—individual rosettes flower once, producing a stalk bearing clusters of pink to magenta star-shaped flowers before dying, while the plant persists through the continuous production of offsets that form spreading clonal colonies. The specific epithet 'arachnoideum' derives from the Latin for spider, referencing the cobweb-like pubescence. This species has been widely cultivated in rock gardens and alpine gardens worldwide for its ornamental appeal and extreme hardiness. Several varieties and cultivars exist, showing variation in hair density and leaf coloration. Its conservation status has not been formally evaluated by the IUCN, though it remains common throughout its native range.