Sempervivum arachnoideum
Common name: Cobweb houseleek · Cobweb hens and chicks
Sempervivum arachnoideum is a small evergreen succulent native to the Alps, Apennines, Pyrenees, and Carpathians of southern and central Europe. Its tight rosettes of red-tipped leaves are covered in fine white hairs that stretch like a cobweb across the leaf tips, giving the plant its common name. In summer, mature rosettes produce short stalks of starry pinkish-red flowers, after which the rosette dies and is replaced by its many offsets. It is prized in rock gardens, troughs, and green roofs for its distinctive webbed look.
Care summary
Sun
Full sun to light shade
Water
Low; very drought tolerant, keep dry in winter
Soil
Gritty, poor, sharply drained soil
Hardiness
Zones 4–8
Mature height
About 8–10 cm (0.25–0.3 ft)
Pet safe
Yes, non-toxic to cats and dogs
Difficulty
Easy
Propagation
Propagate by the offsets (chicks) each rosette produces on short stolons: detach them once they reach a reasonable size, let the break dry briefly, and set them on gritty soil where they root quickly. This is essential since each rosette dies after flowering.
Fun facts
- The white hairs forming the "cobweb" help shield the rosette from intense alpine sun and reduce water loss.
- The epithet "arachnoideum" comes from the Greek for "spider", referring to the web-like hairs.
- It grows wild on rocky ledges and screes in the mountains, often rooting in cracks with almost no soil.
- Like other sempervivums, the flowering rosette dies after blooming, but each plant leaves behind numerous chicks.