Sempervivum arachnoideum subsp. tomentosum (C.B.Lehm. & Schnittsp.) Schinz & Thell.
Woolly Cobweb Houseleek, Cobweb Hen and Chicks
Sempervivum tomentosum, Sempervivum laggeri, Sempervivum arachnoideum var. laggeri, Sempervivum webbianum
Sempervivum arachnoideum subsp. tomentosum is a mat-forming succulent that forms rosettes of fleshy, obovate, mid-green to red leaves, densely covered in white, cobweb-like hairs. The rosettes grow up to 1.6 inches (4 cm) in diameter. Flowers are pink, star-shaped, up to 0.6 inches (1.5 cm) in diameter, and borne in flat cymes on stems up to 6 inches (15 cm) tall.
USDA hardiness zone 4a to 10b: from −30 °F (−34.4 °C) to 40 °F (+4.4 °C).
Because of the variability of Cobweb Houseleek, they easily adapt to the local conditions, and due to the small gene pool, they become a form or variety quite quickly, perfectly adapted to the local conditions of heat and cold as well as the amount of snow or rain and at which times of the year.
Relatively easy to grow in a container or a rock garden, scree bed, wall crevice, trough, or alpine house. They are ideal in so many ways, as they quickly start to form very tight clusters of rosettes, filling in Sempervivum walls, mosaics, and topiary, and their shallow yet fibrous root systems hold soil in place even in vertical plantings. After the plant blooms and sets seed, it will die, but many offsets will take its place.
Plant in well-drained succulent soil mix in full sun to light shade. Water regularly during the growing season and allow the soil to dry out before watering again. Water very little during the winter months. See more at How to Grow and Care for Cobweb Houseleek (Sempervivum arachnoideum).
Native to the mountains of central and southern Europe.
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Sempervivum arachnoideum ssp. tomentosum: This S. arachnoideum is very heavily cobwebbed with 3/4" plants. It gets many tiny chicks on short stolons. They make nice neat clumps and have a slight rosy cast. Can flush lightly purple in spring.
After trials by the Royal Horticultural Society, S. arachnoideum tomentosum earned the Award of Garden Merit in 1993 and was reconfirmed in 2008.
Hens & Chicks need plenty of outdoor sunlight to show their best colors and maintain a tight rosette form. They thrive in gritty, well-draining soils and pots with drainage holes. They produce new offsets or "chicks" on stolons. These chicks can be lefts to form tidy clusters or removed to share and transplant.
Sempervivum do most of their growing in the spring and summer, and will thrive with weekly watering and afternoon shade if temperatures exceed 85F. They are incredibly frost hardy and will happily overwinter under a blanket of snow. Protect from heavy rains and standing water to prevent rot.
Sempervivum arachnoideum subsp. tomentosum is an ornamental mat-forming, evergreen perennial succulent with rosettes up to 4 cm in diameter, of fleshy, obovate, mid-green to red leaves, densely covered in white, cobweb-like hairs. The star-shaped, pink flowers up to 1.5 cm in diameter are borne in flat cymes on stems up to 15 cm tall.
Scientific Name: Sempervivum arachnoideum subsp. tomentosum (C.B.Lehm. & Schnittsp.) Schinz & Thell.
Synonyms: Sempervivum tomentosum, Sempervivum laggeri, Sempervivum arachnoideum var. laggeri, Sempervivum webbianum.
Common Names: Woolly Cobweb Houseleek, Cobweb Hen and Chicks.
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.
|Sempervivum arachnoideum subsp. tomentosum (laggeri)||Accepted|
|Other Details:||Form of arachnoideum subsp tomentosum named after the botanist Lagger.|
|History of species or Cultivar:||S. laggeri Schott ex Hallier (1892) / S. arachnoideum ssp. tomentosum (C. B.Lehmann & Schnittspahn) Schinz & Thellung|
|Awards:||AGM: 1993 |
|Soil type:||Dry |
Loamy / Medium
Sandy / light
Other: The soil type will depend on what your weather conditions are like. Just make sure it drains well.
|Water:||Very low |
Does not like wet feet
|Pests and Diseases:||Pest resistant |
|Plant Habit:||Cactus/Succulent |
|Life cycle:||Perennial |
|Sun Requirements:||Full Sun to Partial Shade |
|Minimum cold hardiness:||Zone 4a -34.4 °C (-30 °F) to -31.7 °C (-25 °F) |
|Flower Time:||Summer |
Late summer or early fall
Other: It may be several years before it blooms
|Uses:||Provides winter interest |
|Wildlife Attractant:||Bees |
|Resistances:||Deer Resistant |
|Propagation: Seeds:||Provide light |
Stratify seeds: Stratifying seeds may improve germination, but is not required
Suitable for wintersowing
Sow in situ
Will not come true from seed
|Propagation: Other methods:||Offsets |
|Containers:||Suitable in 1 gallon |
Suitable in 3 gallon or larger
Needs excellent drainage in pots
Sempervivum arachnoideum L. subsp. tomentosum
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