A large genus of herbaceous perennials in the Saxifragaceae family originating from Alpine ecosystems in temperate zones of the Northern Hemisphere. Many are typical arid-zone plants with modified leaves (succulent, needle-like, hairy) to reduce evaporation when growing in exposed sites although there are a few members of the family that thrive in wet meadow habitats. They are usually mat-forming and have panicles or cymes of starry flowers emerging above the base. Cultivated varieties are often grown in alpine houses.