Cobweb houseleek

Sun

Full sun; light afternoon shade can help in hot inland gardens. Avoid humid, poorly ventilated sites.

Water

Low once established. Water new plants lightly while they root; thereafter let the soil dry between waterings. Containers may need occasional watering during prolonged dry weather.

Soil

Lean, gritty, sharply drained soil. Suitable for rocky crevices and containers with drainage holes; avoid heavy clay and moisture-retentive compost.

Height

0.1-0.25 ft (0.03-0.08 m) in leaf; flower stems reach about 0.3-0.7 ft (0.1-0.2 m)

Spread

0.5-1 ft (0.15-0.3 m), gradually extending farther through offsets

Flowers

Pink to rose-red, star-shaped flowers on upright stems in summer. Each flowering rosette dies afterward, leaving its offsets.

Foliage

Evergreen. Small, fleshy, pointed leaves form compact green rosettes, often flushed red. Fine white hairs stretch between the leaf tips like cobwebs.

Growth

Slow to moderate; forms a spreading cushion of small rosettes

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   0.2 ft (0.06 m)

   full size

About 8 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Growth rate

Slow

• Plant with the base of each rosette above the soil surface, not buried.
• Water the soil rather than repeatedly soaking the rosettes, and let it dry between waterings.
• Use a thin gravel mulch to keep lower leaves away from damp soil; avoid bark mulch around the crowns.
• Do not feed plants in the ground routinely; give container plants only an occasional weak feed in spring if growth is poor.
• Keep pots freely draining and shelter them from persistent winter rain where necessary.
• Detach and replant offsets in spring or early summer if cushions become crowded.

Pruning. No routine pruning is needed. After flowering, remove the spent stem and dead parent rosette without disturbing the surrounding offsets; gently remove loose dead leaves when dry.

Spring

Remove loose dead leaves and check that winter moisture has not softened the crowns.

Spring

Plant or repot into a gritty mix, keeping rosette bases above the soil.

Early summer

Detach well-developed offsets and root them in small pots of gritty compost.

Summer

Water containers only when the mix has dried; check beneath rosettes for mealybugs.

Late summer

Remove spent flower stems and dead flowering rosettes, leaving healthy offsets.

Autumn

Clear fallen leaves and check drainage before wet weather arrives.

Winter

Keep containers out of standing water and protect them from prolonged rain if the mix stays wet.

• Tuck into sunny rock-garden crevices, where the small rosettes follow the contours of stone.
• Plant in shallow troughs with other hardy houseleeks for contrasting rosette colours and textures.
• Use along the front of a sunny gravel bed with low stonecrops and dwarf pinks.
• Grow in small terracotta containers beside steps or seating, where the cobwebbed foliage can be seen closely.

Garden styles it suits: Alpine rock garden, Dry gravel garden, Desert / xeriscape, Low-maintenance, Small-space and Contemporary minimal.

Plant it with: Common houseleek, White stonecrop, Goldmoss stonecrop, Maiden pink and Creeping thyme.

Wildlife: Open summer flowers provide nectar and pollen for visiting bees and other insects. The foliage is not a significant wildlife food source.

• Crown or root rot: rosettes become soft or collapse in wet soil. Remove affected plants, improve drainage and replant healthy offsets in fresh gritty mix.
• Mealybugs: white cottony clusters hide between leaves or around roots. Isolate affected pots, remove visible insects and use a treatment labelled for mealybugs on ornamental succulents if needed.
• Vine weevil larvae in containers: root damage leaves rosettes loose or wilted. Inspect the root ball, remove larvae and use an appropriate biological control when conditions suit it.
• Open, stretched rosettes: insufficient light weakens the compact shape. Move plants gradually into a sunnier position.

Not known to be toxic to people, cats, dogs or horses. No part is recognised as poisonous, but it is not a food plant; eating it may cause stomach upset, and information specific to horses is limited.

• Common houseleek (Sempervivum tectorum)

  Usually has larger rosettes with broader leaves and lacks the conspicuous web of white threads stretched between leaf tips.

• Mexican snowball (Echeveria elegans)

  Has broader, spoon-shaped, pale blue-green leaves with a powdery coating rather than cobweb threads. It is also much less cold-hardy.

Sempervivum means 'always living', referring to its persistent evergreen rosettes, while arachnoideum means 'spider-like', describing the cobweb of hairs across the leaves.

Propagation. Detach offsets in spring or early summer, preferably once they have small roots, and set them on gritty compost with their bases just touching the surface. Water sparingly while they establish. Seed is possible, but seedlings may vary, especially where other houseleeks grow nearby.

Accepted botanical name

Sempervivum arachnoideum

Native range

Austria, Corse, France, Germany, Italy, Spain and Switzerland.

Measured

Average height 14 cm.

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.