Cobweb Houseleek
Sempervivum arachnoideum · Crassulaceae
📷 Kulawik.pl · CC BY-SA 4.0
The gardener's calendar
In autumn, ease off feeding and take the chance to clean up around cobweb houseleek and prepare for winter.
ID card
- Foliage
- Evergreen, fleshy, arranged in a compact rosette
- Flowering
- June to July, small pale pink or red flowers
- Mature size
- 10 to 15 cm tall, 15 to 20 cm spread
- Growth
- Very slow
- Hardiness
- Very hardy (down to -20°C)
- Origin
- Alps and Pyrenees, rocky high-altitude areas
- Foliage type
- Leaves covered with a fine white web (fine hairs)
✓ Taxonomy verifiedSource: AI estimate · hardiness: reliability high.
Expert tips
The key tip
Fears winter moisture far more than cold. In waterlogged soil, it rots.
The common mistake
Planting it in a regular bed with regular watering: it wastes away suffocated, not from hunger.
The pro's trick
In pots, use very well-draining substrate (half potting soil/half perlite or fine gravel); apply fine mineral mulch (pumice) at the collar.
Care
Watering
Very moderate: the cobweb houseleek is exceptionally drought-resistant. Water lightly in summer, once every 15 to 20 days, and barely at all in winter. The soil must dry completely between waterings. Excess water causes rosette rot.
Light
Place it in direct sun for at least 6 hours a day to maintain its color and compact shape. In partial shade, it will become leggy and lose its characteristic appearance. This plant loves hot, open exposures.
Soil and substrate
Use very well-draining soil: mix succulent potting soil with gravel or perlite (70% soil, 30% mineral). Heavy or overly rich soil causes legginess. A pot with drainage holes is essential to prevent water buildup.
Pruning and propagation
No pruning is necessary. The cobweb houseleek naturally multiplies through "baby" rosettes that form around the mother plant. Remove them after flowering (the mother rosette dies after blooming) and replant them in well-draining substrate.
Fertilizer
Very undemanding in nutrients, this alpine plant needs virtually no fertilizer. A very diluted application in spring is enough if you really want to feed it. Excess fertilizer causes unbalanced growth and weakens the plant.
Diseases and pests
Very resistant and rarely sick in dry conditions. The main enemy is excessive moisture, which causes rot. Indoors, spider mites are possible in very dry air. Inspect regularly and ensure good ventilation.
Did you know?
The name "arachnoideum" comes from the Latin "aranea" (spider): the fine white filaments covering its leaves indeed resemble a spider's web. This botanical adaptation protects the plant from the intense solar radiation of the alpine heights where it naturally grows, reducing evaporation and filtering ultraviolet rays.
Where to buy it
Plant in spring, once all risk of frost has gone. Pick a plant with healthy foliage and roots that are not exposed. Best time: from April to June.
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Tips generated and checked by Viridia — adapt them to your local climate.