Cussonia is a genus of roughly 20–22 species of shrubs and trees in the family Araliaceae (order Apiales), native to sub-Saharan Africa, Yemen, and the Comoro Islands. The genus has its center of diversity in South Africa and the Mascarene Islands, and is one of the most visually distinctive plant groups of the African flora.
Plants grow with a striking palm-like habit: stems are squat to lanky, and the leaves are clustered in conspicuous umbrella-shaped arrangements at the tips of long, erect branches. Leaves are carried on elongated petioles with prominent stipules and are highly variable in shape — often palmately compound with variable leaflets, but sometimes simple or palmate. The stems and underground parts are succulent, and the bark is frequently corky, adaptations suited to fire-prone and seasonally dry environments. Dense, often spiked inflorescences carry small flowers with typically 5 greenish petals.
The genus is closely related to the Afro-Malagasy and Asian genus Schefflera and the Afrotropical Seemannaralia, which share several of its features: leaves borne at branch tips, inflorescences on terminal branches or stems, and reduced leaf complexity around developing inflorescences. The genus name honors Pierre Cusson, an eighteenth-century French botanist.
Species range from lowland forests and woodlands to montane grasslands at over 2,000 metres. Notable members include Cussonia arborea, Cussonia spicata (the common cabbage tree of southern Africa), and several narrow-range endemics in South Africa such as Cussonia gamtoosensis and Cussonia arenicola.
Etymology
The genus name Cussonia commemorates Pierre Cusson (1727–1783), a French botanist and physician from Montpellier who made contributions to the study of umbellifers and related plants in the family Araliaceae.
Distribution
Cussonia species are indigenous to sub-Saharan Africa, Yemen in the Arabian Peninsula, and the Comoro Islands, with the greatest diversity concentrated in South Africa and the Mascarene Islands. They occupy a wide range of habitats — grasslands, woodlands, and forests — from sea level to above 2,000 metres altitude.
Ecology
Species grow across grasslands, woodlands, and forests over a broad altitudinal range (sea level to over 2,000 m). Succulent stems and corky bark are adaptations associated with fire-prone and seasonally dry African environments. Their dense inflorescences attract small pollinators, and the genus is recognized as a conspicuous and easily identifiable component of the African landscape.
