The main attraction of these plants is their colorful rosettes of leaves. They range from bright yellow through various shades of green, grey, pink, purple, red, orange, and brown, to almost black in some varieties. The leaves may be dull, glossy, or covered with soft down or longer hairs. The tiny silvery hairs are commonly found along the leaf margins, and in many varieties, the leaf tips bear a tuft of longer hairs that can form a "cobweb" over the surface of the rosettes. Leaf shape can also vary from short, succulent, almost round leaves to long, tapering, finely pointed ones.
The rosettes are most striking in the spring and summer, but even in the winter, when growth stops, many varieties remain attractively colored. The endless range of different leaf shapes, colors, and textures makes this group so interesting to succulent enthusiasts.
Houseleeks reproduce vegetatively by producing a cluster of offsets around the base of the plant. These are often borne on the ends of long stolons, and they can either be left to root around the main plant to form a cushion of rosettes or be detached and grown separately.
In their second or third year, most rosettes will stop producing offsets and begin the process of flowering. The first sign of this is usually a deepening of the color of a large rosette followed by elongation of the main stem. This grows for 4 to 12 inches (10 to 30 cm) and produces a large cluster of attractive pink, purple, yellow, or white flowers.
The two genera are most easily distinguished by their flowers. In Sempervivum, the flowers are star-shaped with 8 to 16 petals. The most common colors are shades of pink or red, although some have cream or yellow flowers.
Rosularia flowers typically have 6 to 8 petals, but the flowers open wide and are usually cream-colored or pale yellowish.
Most flowers produce fertile seeds, but hybridization is very common, so to propagate known varieties, it is essential to use offsets rather than seeds.
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