How to Grow Cobweb Houseleek
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Cobweb Houseleek
Sempervivum arachnoideum 'Cobweb'
succulentSempervivum 'Cobweb' is a cold-hardy evergreen succulent forming tight rosettes densely covered with silvery cobweb-like hairs that give the plant its distinctive appearance. The rosettes typically reach 2-3 inches in diameter and produce pale pink to red star-shaped flowers on tall inflorescences in summer. This compact, low-growing cultivar is ideal for rock gardens, container growing, and alpine displays.
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Example Cobweb Houseleek timeline · Pittsburgh, PA (Zone 6b)
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Plant Cobweb Houseleek
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Cobweb Houseleek
Late summer into fallBefore the first fall frost (≈ Nov 8)
Sample dates for Pittsburgh, PA. Sign up to get exact Cobweb Houseleek dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 3-8, extremely cold-hardy and tolerates freezing temperatures
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Get my Cobweb Houseleek timeline →Growth Stages
Rosette Formation
3-6 months from offsetYoung plants develop tight, compact rosettes with characteristic silvery webbing on leaf surfaces; rosettes 1-2 inches in diameter
Ensure excellent drainage; avoid overwatering. Provide full sun exposure to enhance webbing visibility and compact growth habit.
Mature Rosette
6+ months to 1-2 yearsFully formed 2-3 inch rosettes with dense cobweb-like hairs covering leaves; rosettes may darken to reddish tones in cool seasons or bright light
Maintain strict watering discipline. Allow rosettes to touch if space permits—they are drought-tolerant and benefit from air circulation. Minimal fertilizer needed.
Flowering
4-6 weeksTall inflorescence (4-6 inches) emerges from mature rosette, bearing pale pink to red star-shaped flowers in loose clusters
Flowering occurs typically in early to midsummer. Allow flower stems to develop fully; do not remove prematurely. Provide consistent but sparse water during bloom.
Seed Production & Pup Development
6-12 weeks post-floweringAfter flowering, the parent rosette dies back (monocarpic nature). Surrounding rosettes or new offsets (pups) continue to grow and develop around the base
Remove spent flower stalks. The dying mother rosette can be carefully removed once completely dried. Pups will fill in the space and eventually mature.
Dormancy & Winter Survival
3-4 months (November-March)Rosettes enter dormancy in late fall/winter, often developing deeper red or burgundy coloration. Leaves may appear slightly shriveled but plants are not harmed
Do not water during dormancy. Ensure drainage is excellent to prevent rot from winter moisture. Protect from excessive moisture and wet snow if grown outdoors.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Remove affected rosettes; spray with isopropyl alcohol or insecticidal soap. Improve air circulation and reduce humidity.
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Caused by overwatering and poor drainage. Repot in fresh, dry soil mix. Remove rotted portions. Allow soil to dry completely before watering.
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Increase air circulation and humidity slightly (mist occasionally). Spray with insecticidal soap if severe. Remove heavily infested rosettes.
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and
Remove by hand, especially in damp conditions. Use copper tape barriers around containers. Avoid excessive watering which encourages slugs.
Uses
Ornamental Container & Alpine Gardens
HouseholdSempervivum 'Cobweb' is prized for its striking appearance in succulent containers, rock gardens, troughs, and alpine displays. Its compact size and cold hardiness make it ideal for outdoor container arrangements that withstand winter frost. [source]
Pollinator-Friendly Flowering Plant
WildlifeThe summer flowers attract pollinators including bees and butterflies, providing early season nectar and pollen. Flowering extends the garden's appeal beyond foliage interest. [source]
Propagation & Plant Collecting
CraftSempervivum 'Cobweb' is easily propagated from offsets, making it an excellent plant for collectors, propagation hobbyists, and for creating living wall or vertical garden arrangements. Its slow growth and long lifespan reward patient gardeners. [source]
Xeriscaping & Low-Maintenance Landscaping
HouseholdAs an extremely drought-tolerant and cold-hardy succulent requiring minimal water and care, Sempervivum 'Cobweb' is perfect for water-wise xeriscape gardens, drought-prone regions, and hands-off landscape designs. [source]
Traditional Herbal Use
MedicinalSempervivum species have been traditionally used in European folk medicine for skin complaints and minor wounds, though modern scientific evidence is limited. The succulent leaves contain compounds with potential antimicrobial properties. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Not harvested for food or foliage. For propagation: Gently detach mature offsets (pups) from the base in spring or summer. Allow offset wounds to air-dry for 2-3 days before planting in well-draining succulent mix. Rosettes produce seeds after flowering; collect dried seed pods and sow on gritty seed mix, barely covering seeds with sand.
Fun Facts
- 🌱 The cobweb-like hairs (trichomes) covering the leaves serve multiple purposes: they reflect excess sunlight to prevent sun damage in alpine environments, help conserve moisture, and give the plant its distinctive silvery appearance that becomes more pronounced in cool weather.
- 🌱 Sempervivum 'Cobweb' is monocarpic, meaning each rosette flowers only once in its lifetime, then dies—but not before producing numerous offsets that will mature and bloom in subsequent seasons, ensuring the plant colony persists indefinitely.
- 🌱 The genus name Sempervivum comes from Latin 'semper' (always) and 'vivus' (living), reflecting the plant's remarkable hardiness and the old superstition that these plants protect houses from lightning and fire—they were commonly grown on rooftops in medieval Europe.
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