Cobweb house-leek: complete guide

Overview

Cobweb house-leek (Sempervivum arachnoideum) is a spectacular alpine succulent from the Crassulaceae family, native to northern Spain through the Alps to the Apennines. Renowned for its extraordinary appearance - delicate white filaments creating cobweb-like patterns between leaves - this plant brings intrigue and beauty to any alpine collection. It is perfect for stone troughs, rock gardens, alpine screes, and living roofs.

Appearance and bloom cycle

Cobweb house-leek grows as tight, densely packed rosettes measuring 2-3 cm diameter. Leaves are green with red tinges, covered with characteristic fine white filaments spanning between leaves, exactly mimicking spiderweb. This creates an otherworldly, almost surreal appearance. In June and July, red to purple flowers appear on 10-15 cm tall flower stems. After flowering, the mother rosette dies, while daughter offsets continue growing.

Ideal location

Cobweb house-leek performs best in full sun. At least 5-6 hours of direct sunlight daily is essential for good color development and to maintain the cobweb effect. In shade, the white webbing largely disappears. The plant tolerates mountain winds and cold air currents well. Protection from waterlogged conditions matters far more than frost protection.

Soil requirements

Cobweb house-leek demands excellent drainage and poor, infertile soil. Sandy, gravelly soils rich in grit are ideal. Heavy clay is entirely unsuitable. Drainage is critical: one wet winter can kill the plant. The plant thrives in extremely nutrient-poor soils. A soil pH between 6.0 and 7.5 is acceptable.

Watering

Cobweb house-leek is one of the most drought-tolerant succulents. Water is needed only in the first growing year after planting. Once established, the plant accepts very extended droughts. Heavy watering causes immediate root rot. In wet winters, drainage must be perfect. Never water is always better than regular watering.

Pruning

Pruning is virtually unnecessary. Dead or shriveled leaves can be gently removed. After flowering, the blooming rosette naturally dies, which is normal. Remove the dead rosette carefully to make room for new offsets. Occasional brushing can prevent moss accumulation on rosettes.

Maintenance calendar

Spring (April-May): Plant carefully, do not water unless extremely dry. Summer (June-July): Observe and enjoy, no care needed. Autumn (August-September): Remove dead flowering rosettes, check drainage. Winter (October-March): No maintenance; drainage is critical.

Winter hardiness

Cobweb house-leek is hardy in USDA zones 3-9, surviving temperatures to -20°C. The plant is evergreen and decorative in winter. Frost poses no threat; waterlogged conditions in winter are deadly. Good drainage matters far more than any other factor.

Companion plants

Cobweb house-leek pairs perfectly with other alpine sempervivum species and dry rock plants. Beautiful alongside sedums, saxifrages, and other choice alpines. In green roofs, combine with other low alpine foliage plants. Moisture-loving species are entirely unsuitable.

Closing

Cobweb house-leek is a truly unique ornament in any alpine collection or rock garden. Its distinctive white webbing makes it a conversation piece. Visit gardenworld.app for more ideas to integrate alpine succulents effectively into your garden design. With virtually zero care and years of decorative value, cobweb house-leek deserves a special place in every sunny rock garden or alpine trough.