Sempervivum arachnoideum, the cobweb house-leek, is a species of flowering plant in the family Crassulaceae, native to the Alps, Apennines and Carpathians. Growing to 8 cm tall by 30 cm wide, it is a rosette-forming succulent perennial, valued in cultivation for its ability to colonise hot, dry areas via offsets.
The specific epithet arachnoideum refers to its furry central rosettes (long ciliate leaf margins), resembling spider webs.
It flowers in July, with pink flowers that are raised on stems and are hermaphroditic (having both male and female organs).
Medicinal benefits of Sempervivum arachnoideum (Cobweb Houseleek):
- The leaves of Cobweb Houseleek are emollient, hemostatic, ophthalmic and sedative.
- The crushing 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.
How to grow and maintain Sempervivum arachnoideum (Cobweb Houseleek):
It thrives best in full sun to light shade. In indoor an east or west-facing window where they receive four to six hours of sunlight is ideal.
It needs excellent drainage. Poor, sandy soil would be just fine. You could work some peat into heavier soil, to lighten them and improve drainage.
Water regularly during the summer and spring. keep the soil evenly moist but not soggy. You can allow the topsoil to become slightly dry between each watering. Reduce water in the winter.
It prefers an average summer temperature 65 degrees Fahrenheit – 70 degrees Fahrenheit / 18 degrees Celsius – 21 degrees Celsius. In winter, some varieties can withstand temperatures down to freezing.
Fertilize with a controlled-release fertilizer at the beginning of the season or weekly with a weak liquid solution. Use a balanced 20-20-20 fertilizer at 1/4 strength on mature plants, and a fertilizer with less nitrogen on young plants.
Re-pot as needed, preferably during the warm season. To re-pot, a succulent, make sure the soil is dry before repotting, then gently remove the pot. Knock away the old soil from the roots, making sure to remove any rotted or dead roots in the process. Treat any cuts with a fungicide. Place the plant in its new pot and backfill with potting soil, spreading the roots out as you re-pot. Leave the plant dry for a week or so, then begin to water lightly to reduce the risk of root rot.
Pests and Diseases:
It has no serious pest or disease problems. Cobweb Houseleek can get vine weevil and may be subject to rust.
It can be easily propagated by seed sown in spring or root offsets in spring. Sempervivum earned their famous name “Hen and Chicks” from their growth habit. The mother plant, or hen, sends off numerous offsets, which will cluster around her base like chicks. These offsets can be easily re-potted, or the plants can be left to form a clumping mat.