Sempervivum arachnoideum Arctic White ('Belsemcob2') (Colorockz Series)

RHS Plant Profile

cobweb houseleek [Arctic White]

Synonyms

Sempervivum arachnoideum 'Belsemcob2'

Cactus Succulent

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An evergreen succulent, forming cushions of rosettes of fleshy green leaves tipped with fine white hairs. Rosettes are densely covered with webbing from spring to autumn. Tall spikes of starry pink flowers are produced from mature rosettes in summer; these die off after flowering and are replaced by new offsets

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity: 2–5 years
Max Spread: 0.1-0.5 metres
Max Height: 0.1-0.5 metres

Growing Conditions

Chalk Loam Sand

Moisture: Well–drained
pH: Acid or Alkaline or Neutral

Position

Full sun

Aspect: South–facing or West–facing
Exposure: Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

H1A: under glass all year (>15C)
H1B: can be grown outside in the summer (10 - 15)
H1C: can be grown outside in the summer (5 - 10)
H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
H4: hardy through most of the UK (-10 to -5)
H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
H6: hardy in all of UK and northern Europe (-20 to -15)
H7: hardy in the severest European continental climates (< -20): H6
Drought Resistance: Yes

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Crassulaceae
Native to GB/Ireland: No
Foliage: Evergreen
Habit: Matforming
Genus: Sempervivum are evergreen perennials forming mats of fleshy-leaved rosettes, often attractively coloured, with star-shaped pink or pale yellow flowers in summer
Name Status: Trade

How to Grow

Cultivation

Grow in poor to moderately fertile, sharply drained soil in full sun. In pots use a 50:50 mix of peat-free, loam-based potting compost and grit. Protect from excessive winter wet. See hardy cacti and succulent cultivation

Propagation

Propagate by rooting offsets in spring and early summer

Suggested planting locations and garden types

City and courtyard gardens
Cottage and informal garden
Gravel garden
Houseplants
Patio and container plants
Rock garden
Conservatory and greenhouse

Pruning

No pruning required

Pests

May be susceptible to vine weevil larvae and sempervivum leaf miner

Diseases

May be susceptible to rust diseases