Cistaceae

The Cistaceae are a small family of plants (the rock-rose or rockrose family), mostly shrubs, which are profusely covered by flowers in the spring and summer. This family consists of about 170-200 species in eight genera that are not very distinct, distributed primarily in the temperate areas of Europe and the Mediterranean basin, but also found in North America; a limited number of species are found in South America. Most Cistaceae are subshrubs and low shrubs, and some are herbaceous. They prefer dry and sunny habitats. Cistaceae grow well on poor soils, and many of them are cultivated in gardens.

They often have showy yellow, pink or white flowers, which are generally short-lived. The flowers are bisexual, regular, solitary or borne in cymes; they usually have five, sometimes three (Lechea), petals. The petals are free, usually crumpled in the bud, and sometimes in the open flower (e. g. Cistus incanus). The flowers have five sepals, the inner three of which are distinctly wider, and the outer two are narrow and sometimes regarded as bracteoles. This sepal arrangement is a characteristic property of the family.

The stamens are numerous, of variable length, and sit on a disc; filaments are free. The ovary is superior, usually with three carpels; placentation is parietal, with two or more ovules on each placenta. The fruit is a capsule, usually with five or ten valves (three in Helianthemum). The seeds are small, with a hard, water-impermeable coating, weighing around 1 mg.

Recently the neotropical species Pakaraimaea dipterocarpacea, formerly placed in the family Dipterocarpaceae, has been placed in the Cistaceae, following APG IV (2016). Unlike the rest of the family, it is a large tree, with specimens to over 130 cm trunk diameter reported. It has also been suggested that it might be better treated in its own monotypic family.