Cobweb houseleek Sempervivum arachnoideum
Cobweb houseleek (Sempervivum arachnoideum) is an evergreen perennial groundcover in the Crassulaceae family, native to Mountains of southern Europe: the Alps, Pyrenees, Apennines and Carpathians. It grows 3–10 cm (1–4 in) tall and 15–30 cm (6–12 in) wide, wants full sun and low water, and is hardy to about -30 °C (-22 °F). Space plants about 15 cm (6 in) apart.
Plan Cobweb houseleek in your garden →
Free. Draw your beds, then watch it grow through the year in 2D and 3D.
Cobweb houseleek at a glance
| Type | Perennial groundcover, evergreen |
|---|---|
| Family | Crassulaceae |
| Mature height | 3–10 cm (1–4 in) |
| Mature spread | 15–30 cm (6–12 in) |
| Spacing | 15 cm (6 in) centre to centre |
| Sun | Full sun, at least 6 h of direct sun a day |
| Water | Low; drought tolerance high, waterlogging tolerance none |
| Soil pH | 5.5–8 |
| Cold hardiness | About -30 °C (-22 °F) once established (roughly USDA zone 4) |
| Heat stress | Likely above about 34 °C (93 °F) |
| Flowering | from about June for 4–6 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | High |
| Pollinator value | Moderate |
| Edible | Not grown as food |
| Native to | Mountains of southern Europe: the Alps, Pyrenees, Apennines and Carpathians |
| Common in gardens of | 🇬🇧 United Kingdom, 🇩🇪 Germany, 🇫🇷 France, 🇮🇹 Italy, 🇳🇱 Netherlands, 🇸🇪 Sweden, 🇵🇱 Poland, 🇺🇸 United States, 🇨🇦 Canada |
Is Cobweb houseleek toxic?
- People: not known to be toxic
- Cats: not known to be toxic
- Dogs: not known to be toxic
Not poisonous.
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Cobweb houseleek
No well-documented helpful pairing. Group it with plants that like full sun and low water.
Questions about Cobweb houseleek
- How far apart should I plant Cobweb houseleek?
- About 15 cm (6 in) apart, centre to centre. A mature plant spreads 15–30 cm (6–12 in).
- Does Cobweb houseleek need full sun?
- Full sun: at least 6 hours of direct sun a day.
- How much water does Cobweb houseleek need?
- Low water. Drought tolerance is high and waterlogging tolerance none.
- How cold-hardy is Cobweb houseleek?
- It tolerates about -30 °C (-22 °F) once established, roughly USDA zone 4.
- When does Cobweb houseleek flower?
- From about June for 4–6 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is Cobweb houseleek poisonous to cats and dogs?
- For cats it is not known to be toxic; for dogs not known to be toxic; for people not known to be toxic. Not poisonous.
- What grows well with Cobweb houseleek?
- There is no well-documented companion pairing for Cobweb houseleek. Group it with plants that like the same sun (full sun) and water (low).
Sources and evidence
Evidence grade A (A: strong evidence).
- Plants of the World Online (taxonomy, native range), Royal Botanic Gardens, Kew
- RHS Find a Plant (plant profiles and growing guides), Royal Horticultural Society
Notes and assumptions
- Tiny rosettes laced with white threads stretching from leaf tip to leaf tip like cobwebs, spreading into tight clusters by offsets (“hens and chicks”). Hardy to deep frost; grows in troughs, wall tops and roof tiles. Each rosette dies after sending up its pink flowers.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
Related plants
- Stonecrop (sedum) Hylotelephium spectabile
- Jade plant Crassula ovata
- Mexican snowball (echeveria) Echeveria elegans
- Common houseleek Sempervivum tectorum
- Roseroot Rhodiola rosea
- Ghost plant (mother-of-pearl plant) Graptopetalum paraguayense
- Moonstones (sugared almond plant) Pachyphytum oviferum
- Burro’s tail (donkey’s tail) Sedum morganianum