Sempervivum

ARACHNOIDEUM

One of the best-known and most delightful species of the genus, first described by Linnaeus in 1753 Sp. Plant. 465. This species has a very wide distribution: Pyrenees, Alps, Apennines, Carpathians. It is a very variable species as to size of rosettes and the development of the ‘cobweb’, it may be so dense as to form a snowy mass which completely hides the leaves or may be quite thin and almost disappears completely in winter. The colour of the rosette leaves may be deep red or shades of green. The flowers are very attractive being of a bright rose-red colour. All the forms are easy to grow and produce offsets freely. This species hybridises readily with other Sempervivums, producing fertile plants which will cross back with the parents and give rise to an infinity of forms.

The following varieties are only extreme forms of the species and are connected with the type by countless intermediates.

 

S. arachnoideum var. arachnoideum.

Rosettes not usually more than 2 cm in diameter, ovoid or globose; arachnoid hairs variable.

Form No. 1. A clone with ball-shaped rosettes densely covered with white woolly hairs. Rosettes about 1,5 cm in diameter.

Form No. 2. Rosettes 1,5 to 2 cm , yellow-green with less arachnoid hair. Rosettes tinted with orange and red in summer.

 

S. arachnoideum var. arachnoideum ‘Fasciatum’.

A curiosity that is only a deformity, the fasciation is not very stable. The form  No. 2 often produce these abnormal growths.

 

S. arachnoideum var. glabrescens (Willkomm).

Syn S. doellianum (C.B. Lehmann ). Rather flattish rosettes bearing only a small amount of cobweb, even in mid-summer. Rosettes do not usually exceed 1,5 cm in diameter,

 

S. arachnoideum var glabrescens ‘Album’ .

An exceedingly rare form with white flowers.

 

S. arachnoideum var. tomentosum (Lehm. & Schnittsp).

Syn. S. webbianum (HORT.), S. laggeri.

Flattish rosettes with very dense white cobweb, much larger rosettes than the var. arachnoideum, up to 4 cm in diameter. This var. has very fine red-coloured rosettes in spring and early summer. 

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