Sempervivum arachnoideum

Sempervivum arachnoideum, commonly known as the cobweb houseleek, is a species of flowering plant in the Crassulaceae family. It is native to Europe. Its specific epithet, arachnoideum refers to the plant's furry central rosettes, which resemble spider webs.

Description
It is a low-growing evergreen perennial shrub, reaching from 0.1 to 0.15 m tall in complete sun and well-drained soil. Its hermaphroditic flowers are pink in color and raised on elongated stems; they flower in July. Each flower has 8-10 petals. The leaf tips connect with each other in a rosette of about 50 to 60 leaves. Like all species in its genus, S. arachnoideum is a species of succulent plant, and can therefore withstand drought longer than that of other plants. It is common in gardening.

Its chromosome number is 2n= 32.

Distribution and habitat
The plant is naturally distributed in Europe in the Alps,Carpathians, and Pyrenees at altitudes from 300 to 2000 m above sea level. Due to its slow growth and short height, the plant is reliant upon other flowering plants in its habitat, and usually does not compete for resources.

Subspecies
Two suspecies of the cobweb houseleek exist:


 * ssp. arachnoideum comes from the Pyrenees, Alps, and Carpathians and is the more common of the two subspecies. Its rosettes reach up to 12 mm wide.
 * ssp. tomentosum comes from the Pyrenees, Southern Alps, and the Apennines. This subspecies has a more red-colored flower with rosettes reaching 25 mm wide.