How to Grow Cobweb Houseleek

Cobweb Houseleek

Sempervivum arachnoideum

succulent

Sempervivum arachnoideum is a mat-forming succulent known for its distinctive rosettes covered in fine, hair-like webbing that resembles a spider web. It produces tight clusters of fleshy leaves in green to reddish tones and sends up flower stalks with star-shaped pink or red flowers. This alpine native is extremely cold-hardy and drought-tolerant, making it an excellent choice for rock gardens, containers, and green roofs.

Growing Conditions

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Sun: Full sun, 6-8 hours daily; tolerates partial shade but produces tighter, more colorful rosettes in full sun

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Water: Low water needs; water moderately during growing season (spring-summer), then reduce significantly in fall and winter; allow soil to dry completely between waterings; avoid overwatering, which causes root rot

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Spacing: 6-9 inches between rosettes; they spread via offsets and will fill in spaces inches

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Days to maturity: 12-18 months to reach flowering maturity

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Planting depth: Plant at soil level; do not bury the rosette crown

Soil

Type: Well-draining gritty soil, sandy loam with mineral content

pH: 6.0-7.0

Amendments:

Perlite or pumice (30-40% of mix) Coarse sand Gravel Compost (minimal, 10-20%)

Growing Zones

Find your zone →

Thrives in zones 3-9; extremely cold-hardy and suitable for most climates except the hottest, most humid regions

3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a

Growth Stages

Establishment

2-4 weeks

Young rosettes, 0.5-1 inch diameter, with tightly clustered fleshy leaves and visible webbing

Keep soil lightly moist (not wet) for first 2-3 weeks; reduce watering once roots establish; provide bright light

Vegetative Growth

6-12 months

Rosettes expand to 1-2 inches diameter, producing offset 'chicks' at the base; webbing becomes more pronounced

Water sparingly; allow soil to dry between waterings; ensure excellent drainage; no fertilizer needed

Pre-Flowering

2-4 months

Mother rosette reaches 2-3 inches diameter; numerous offsets cluster around base; leaves may deepen in color

Continue minimal watering; expose to cool temperatures in fall to trigger flowering response

Flowering

3-4 weeks

Tall flower stalk (2-4 inches) emerges from center with 10-15 star-shaped pink, red, or pale flowers

Mother rosette will die after flowering (monocarpic); offsets surrounding it will continue growing

Post-Flowering & Division

4-8 weeks

Mother rosette withers; offsets mature and can be separated and replanted independently

Remove dead mother rosette; allow offsets to develop roots (1-2 months) before potting individually

Companion Planting

Plan your garden →

Plant with:

Sedum species Echeveria Saxifrage Armeria maritime (thrift) Thymus (creeping thyme) Delosperma (ice plant) Festuca glauca (blue fescue)

Avoid planting near:

Water-loving perennials Plants requiring frequent watering Tall plants that shade it heavily

Common Pests

Remove affected rosettes; spray with neem oil or insecticidal soap; improve air circulation to prevent recurrence
Improve drainage; reduce watering frequency; repot in fresh gritty soil if affected
Increase humidity slightly; spray with water; use miticide if severe
and
Remove by hand; use diatomaceous earth around plants; avoid excessive moisture

Uses

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Ornamental Succulent Planting

Household

Cobweb houseleek is prized for rock gardens, alpine troughs, living roofs, and container arrangements due to its stunning webbed rosettes and extreme cold-hardiness. Its compact size and architectural form make it an excellent focal point in mixed succulent displays. [source]

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Pollinator Support

Wildlife

The star-shaped pink or red flowers attract bees and other pollinators, providing an early summer nectar source in alpine and rock garden settings. [source]

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Traditional Herbal Use

Medicinal

Sempervivum species have been used in traditional European medicine for treating minor skin irritations, burns, and wounds, though modern evidence is limited. The succulent leaves contain mucilage compounds. [source]

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Green Roof & Living Wall Gardens

Craft

Cobweb houseleek is one of the most reliable plants for extensive green roof systems due to its extreme drought and cold tolerance, minimal maintenance, and shallow root system that reduces structural load. [source]

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Low-Maintenance Container Culture

Household

Ideal for small pots, alpine troughs, and container gardening in sunny locations, requiring minimal water, no feeding, and providing year-round visual interest with seasonal color changes. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Sempervivum is not harvested for food. Offsets can be separated and propagated year-round; best time is late spring to early summer. Gently remove rooted offsets ('chicks') from around the mother rosette, allow cut ends to callus for 1-2 days, then plant in gritty soil. Collect seeds from flower heads after blooming; sow on surface of gritty seed mix in fall or spring.

Fun Facts

🌱 The 'arachnoideum' in its scientific name means 'resembling a spider web,' referring to the distinctive fine white hairs that cover the leaves and create a cobweb-like appearance—this webbing may help reduce water loss and protect against intense alpine sunlight.
🌱 Sempervivum means 'always living' in Latin, referencing its incredible hardiness; cobweb houseleek can survive temperatures down to -40°F (-40°C) and can be left outdoors year-round in most climates.
🌱 Like all Sempervivum species, cobweb houseleek is monocarpic, meaning the mother rosette dies after flowering and producing seeds—but it's not wasteful, as it produces many offset 'chicks' that will mature and flower in subsequent years.

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