Cobweb Houseleek
Sempervivum arachnoideum
Family: Crassulaceae
What it is like
Sempervivum arachnoideum is an evergreen Perennial growing to 0.1 m (0ft 4in) by 0.2 m (0ft 8in). See above for USDA hardiness. It is hardy to UK zone 5 and is not frost tender. It is in leaf all year, in flower in July, and the seeds ripen in August. The species is hermaphrodite (has both male and female organs) and is pollinated by Insects. Suitable for: light (sandy) and medium (loamy) soils and prefers well-drained soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils and can grow in very acid soils. It cannot grow in the shade. It prefers dry or moist soil and can tolerate drought.
Height (m): 0.1
Where it is found
Amongst rocks and stones in the cooler regions of Europe, usually on siliceous soils.
Europe.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 0
Medicine
Rating: 2
The leaves are emollient, haemostatic, ophthalmic and sedative. The crushed plant, or its juice, is applied externally to boils, wounds etc and is also used to stop nose bleeds. The slightly warmed juice has been used to relieve ear inflammations and toothaches can be relieved by chewing on the leaves. When macerated and infused in vinegar, the plant can be used to get rid of warts and corns. The leaves are harvested in the summer and are best used when fresh since they are difficult to dry properly. The leaf pulp is used to make a cooling face mask for reddened or sunburnt skin.
Emollient: Softens the skin, causing warmth and moisture.
Haemostatic: Controls internal bleeding.
Odontalgic: Treats toothache (temporary measure only) and other problems of the teeth and gums.
Ophthalmic: Treats eye complaints.
Sedative: Gently calms, reducing nervousness, distress and irritation.
Skin: Plants used in miscellaneous treatments for the skin.
Other
Rating:
How it is grown
Prefers a well-drained gritty soil in full sun. Succeeds in any sandy soil, doing well in very little soil in rock crevices, walls, paths etc so long as there is sufficient humus. Prefers growing on acid rocks, though it also succeeds on calcareous ones. Established plants are drought tolerant. Strongly dislikes winter wet. Plants are not very tolerant of weed competition. Polymorphic, this species is split into a number of sub-species by some botanists. Individual rosettes die after flowering, but produce a number of offsets that continue to grow. Hybridizes with a number of other members of this genus.
Propagating it: Seed - surface sow in early spring in a cold frame. It usually germinates in 2 - 6 weeks at 10°c. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in the summer if they have made sufficient growth, otherwise grow them on for a further year in pots before planting them out. Division of offsets in spring or early summer. Larger divisions can be planted out direct into their permanent positions. We have found it best to pot up the smaller divisions and grow them on in a lightly shaded position in a cold frame, planting them out once they are well established in the summer. Plants can also be divided in September but these divisions should be overwintered in a greenhouse. Stem cuttings.
Best place to grow: Cultivated Beds; East Wall. In. South Wall. In. West Wall. In.
Habit: Perennial
Hardiness: 4-8
Growth:
Soil: Light (sandy), medium
Shade: No shade
Moisture: Dry, moist