Mat-forming evergreen succulents, that form fleshy-leaved symmetrical rosettes, in shades of green, yellow and red. Occasionally, pink or yellow flowers will appear on thick stems in summer.
Family: Crassulaceae (stonecrop)
Botanical Name: Sempervivum
Common Names: Houseleek
Foliage: Small to medium-sized rosettes of thick fleshy leaves, in red or pale green with a red tinge.
Flowers: Star-shaped yellow or pink flowers are borne on stout stems.
Flowering Period: Late spring to mid summer.
Soil: Well-drained, low fertile, gritty soil (sand or loam), any pH.
Conditions: Full sun for most of the day. Best in a south, east or west facing aspect, in either an exposed or sheltered location.
Habit: Mat forming, low growing.
Type: Evergreen perennial.
Origin: Europe, western Asia, and North Africa.
Hardiness: Fully hardy in most regions of the UK.
Sempervivum are best planted in the spring. Plant
in full sun in a well drained gritty soil. Water well
until established. Top dress with grit and protect
from winter wet.
Houseleeks can be grown in small cracks and crevices that contain the tiniest amounts of soil. All forms do well on the rock garden, scree or gravel beds, wall crevices, pots, containers and alpine troughs. Due to their excellent drought tolerance and low growing habit they are often seen growing on 'green roofs'.
Some rosettes will die after flowering and should be carefully removed. Top dress with grit and protect the whole plant from winter wet.
Do not overfeed. Poor soils promote better leaf colour and firmer rosettes.
One established clumps begin to deteriorate, remove all dead and damaged rosettes and rejuvenate by propagating healthy sections of the plant.
No pruning required. Trim off flower spikes and remove dead or damaged leaves.
Susceptible to rust. Can be affected by vine weevil and sempervivum leaf miner.
Propagate by rooting offsets in spring. Remove non flowering rosettes, insert them in horticultural sand and place in a well aired cold frame. They should root quickly and can be potted up in the summer for planting out the following spring.
All forms are low growing and spreading in nature. Height from 1in to 6in (2.5-15cm), average spread 12in (30cm). Sempervivums may not flower every year in the UK.
S. arachnoideum (cobweb houseleek) has rosettes of red tipped leaves with a white cobweb-like mat of hairs that give the appearance of spidery webs. Tall 6in (15cm) red star shaped flowers in June-July. Height to 1in (2.5cm).
S. ciliosum (syn. ciliatum) has globular grey-green rosettes with yellow flowers in summer. The variety 'Borisii' has hairier rosettes, making them appear almost white.
S. 'Corsair' has clusters of medium-sized, bristly-leaf rosettes. Spring growth starts green and turns deep pink-red in summer/autumn. Produces small pink flowers on stout stems in summer.
S. erythraeum has open rosettes of succulent, ovate, green hairy leaves with a purple tinge. Tall flower spikes carry pink-reddish-purple flowers in summer.
S. cantabricum × giuseppii has bright-green rosettes with dark tips, the central leaves are covered in hairs. Rose-red flowers in summer.
S. 'Gwiazda' is a dense, slow spreading, form with olive green succulent rosettes flushed with red.
S. montanum has soft fleshy green leaves covered by clusters of pale red-purple flowers in June-August. Height to 6in (15cm), spread 12in (30cm).
S. tectorum (common houseleek) forms an attractive mat of mid-green rosettes with reddish-purple tips. Purple flowers on 12in (30cm) stems in summer. Height to 3in (8cm), spread to 12in (30cm). Named forms include: 'Commander Hay' (red leaves with green tips) and 'Calcareum' (grey green foliage and red tips).