This is a small genus of hardy to half-hardy succulents, a few of which make extremely easy houseplants. In fact, the botanical name sempervivum is derived from the Latin meaning always alive. Theare succulent and form tight. symmetrical rosettes, and they have a variety of colours, shapes and textures. Sometimes there are very attractive . Perhaps one of the most popular window-sill species is.V. arachnoideum. the cobweb houseleek. from the Pyrenees. It forms green rosettes, often tinted red. and from around the tips of the is suspended a line, whitish webbing suggesting the common name. for , there is an especially line variety..S. a. tomentosum. with more profuse webbing and larger leaves, but there are also a number of hybrids with other differences in colour and shape and they all soon spread out to form a clump. The Mowers, borne in June and July, are a pretty carmine, but after flowering a rosette dies. This does not matter, since there are usually numerous young ones produced and a plant eventually forms a mat-like spread of growth if unrestricted. The are formed in a starry structure, and are held well above the rosettes on 15cm (6in) clothed with small, succulent leaflets.
.S. tectorum is the roof houseleek. so-called because it often colonizes old stone or tiled roofs of country buildings. It is very variable and there are numerous forms with differences in the leaflet colour. Those with reddish or purplish tints are very attractive as houseplants.
The flowers are pinkish to purple. A popular form called ‘Commander Hay’ is now thought to be a hybrid between this species and ,S. marmoreum. It has exceptionally large rosettes and the leaflets are a delightful, shiny, reddish-purple with green tips. The leaflets are rather spatula-shaped, with a small sharp point at their top edge.
S. soboliferum, now known as Jovibarba sobolifera, the hen and chickens houseleek. is another one popular for window-sills, and is native to Russia and Northern Europe. It has bright green rosettes, tinted orange-red in the best forms, but the greenish flowers are rarely produced. Its special characteristic is the freely-formed baby rosettes that appear over the parent rosette, presumably suggesting the common name. These can be removed and potted separately for. Sxfunekii, a hybrid between.S. arachnoideum and.V. tectorum and possibly.S. marmoreum, is very pretty with rosettes of downy texture and finely hairy, and flowers of a lovely rosy purple colour..s’. tectorum calcareum is attractive for its grey-green colouring, contrasting with purple-tipped leaflets, but unfortunately it rarely flowers. It is a pity that the sempervivums are so overlooked as houseplants. since they are and will withstand considerable neglect. They should be given a bright and are best grown in shallow pans or half pots, which must be well drained. Any of the modern composts are suitable, but add some sharp grit for good . Propagation is easily effected by removing and potting the offsets. This is best done in spring. Pests and diseases are rare.