About 110 species of annuals, perennials and shrubs from Macronesia to Europe and North Africa east to Central Asia, also North and South America. They have alternate, simple leaves and racemose cymes of five-petalled flowers which, in the most garden-worthy species open out flat like small single roses.
Certain species and cultivars have long been standard items on every rock garden list of essential plants. Most of them are too large for the smaller rock garden and they are best displayed in dry walls. Ordinary well drained soil is suitable, ideally somewhat alkaline but this is not essential. A sunny site is essential. Propagation by cuttings in late summer, overwintering the young plants under glass. Seed can be sown in spring but hybrid cultivars seldom come true to type. Large-growing cultivars and species can be cut back after flowering to maintain smaller, more compact plants.