The main attraction of these plants is their colourful rosettes of leaves. These 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 or glossy, or covered with soft down or longer hairs. Small 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 coloured. It is the endless range of different leaf shapes, colours and textures that make this group so interesting to 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 they can 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 colour of a large rosette followed by elongation of the main stem. This grows upwards for 4 to 12 inches (10 to 30 cm) then produces a large cluster of attractive pink, purple, yellow or white flowers.
The three 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.
Jovibarba flowers are yellow, more bell-like and usually have six petals.
Rosularia flowers typically have 6 to 8 petals but the flowers open wide and are usually cream or pale yellowish colour.
Most flowers produce fertile seeds but hybridization is very common so in order to propagate known varieties it is essential to use offsets rather than seeds.
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