This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Leaves usually thick and fleshy, usually in dense rosettes. Parts of the flower in sixes or more. Stamens usually double the number of petals. Species numerous, from the Mediterranean region, Atlantic islands, etc. The name is from semper, ever, and vivo, to live.
1. S. tectorum. House Leek. - This is the tufted plant so frequently seen growing in patches on old houses and outbuildings in this country. Leaves glandular-pubescent, ciliate, obovate-lanceolate, mucronate. Flower-stems about a foot high; flowers dull purple.
Besides the above there are several other species occasionally met with in collections, and some are now employed for bedding purposes. S. calcareum, syn. S. Californicum of gardens, a European species, is the one most commonly employed. This has broad rosettes of oblong glaucous leaves with dark tips and purplish flowers. S. arachnoldeum, avenarium, globi-ferum, Ruthenicum, and many others, are coming into general cultivation.
Grammanthes gentianoides, a native of South Africa, is a pretty dwarf annual about 6 inches high with a profusion of crimson or scarlet flowers tinged with yellow. Cotyledon Umbilicus, the Navelwort or Pennywort, found growing on dry banks and walls, also belongs to this group.