Sempervivum arachnoideum, commonly known as Cobweb Houseleek, is a species in the family Crassulaceae, native to the Alps, Apennines, and the Carpathians.
It is a low-growing succulent that forms a mat of fleshy rosettes up to 1.2 inches (3 cm) in diameter. Leaves are green or reddish, with cobwebby white hairs at the tips. The starry pink flowers are up to 0.4 inches (1 cm) across and appear in flat cymes on up to 5 inches (12.5 cm) tall stems.
Because of the variability, Cobweb Houseleek easily adapts to the local conditions, and due to the small gene pool, it becomes a form or variety quite quickly, perfectly adapted to the local conditions of heat and cold as well as the amount of snow or rain and at which times of the year.
Cobweb Houseleek forms the genetic basis for many named varieties using their unique characteristics to influence growing habits, adaptability, and just plain good looks. It is low-maintenance hardy succulent addition to trough gardens, crevice gardens, hypertufa pinch pots, and many more succulent crafts.
Growing Conditions
Light: Full sun to light shade.
Hardiness zones: USDA Plant Hardiness Zone 5a – 8b.
Soil: Cobweb Houseleek, as with most succulents, needs excellent drainage. Poor, sandy soil would be just fine. You could work some peat into heavier soil to lighten them and improve drainage.
Water: It needs regular watering in the growing season, very little in winter.
General Care
Relatively easy to grow in a container or a rock garden, scree bed, wall crevice, trough, or alpine house. Cobweb Houseleek is ideal in so many ways, as it quickly forms very tight clusters of rosettes, filling in Sempervivum walls, mosaics, and topiary, and their shallow yet fibrous root systems hold soil in place even in vertical plantings. After the rosette blooms and sets seed, it will die, but many offsets will take its place.
Plant Cobweb Houseleek in well-drained soil mix in full sun to light shade. Water regularly during the growing season and allow the soil to dry out before watering again. Water very little during the winter months.
Propagation
Propagate by seed sown in spring or root offsets in spring.
Pests and Problems
Cobweb Houseleek can get vine weevil and may be subject to rust.
Links
- Back to genus Sempervivum
- Succupedia: Browse succulents by Scientific Name, Common Name, Genus, Family, USDA Hardiness Zone, Origin, or cacti by Genus
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