About 100 species of annuals and perennials from the northern temperate zone, mainly in the mountains. The most desirable species are the hummock-forming perennials from the high rock crevices and screes. Most species have small leaves in rosettes, often white or grey-hairy or woolly. The flowers are small, basically primrose-shaped, with a tubular base and five, broad, spreading lobes. They may be solitary or gathered in small umbels, often produced in abundance in spring and early summer.
The easy to grow species are ideal for the rock garden and raised bed. High alpine species need vertical crevices in rock work, a dry wall or scree bed conditions. Some also grow well in holes drilled in lumps of tufa rock. Many species make excellent, if demanding pot plants for the alpine house. All species need sharply drained soil and a site in full sun or partial shade. Cushion-forming species in the alpine house need good ventilation and very little water in winter. Any dead shoots must be carefully removed as soon as possible and there is a lot to be said for the routine application of a fungicide. Aphids can also be a serious problem (hidden in the heart of a cushion) and a systemic insecticide is required. Propagation by seed when ripe or as soon afterwards as possible and kept in a cold frame. Cuttings are best taken in summer or after flowering, using single rosettes or small tufts placed in pure gritty sand.