Succulentopedia Sempervivum arachnoideum 'Robin' – Cobweb Houseleek April 12, 2018 Sempervivum arachnoideum 'Robin' (Cobweb Houseleek) is a strikingly beautiful succulent up to 3 inches (7.5 cm) tall at maturity extending to 8 inches (20 cm) tall…