Mostly perennial herbs with fleshy, jointed stems, occasionally shrubs or climbers. Rootstock mostly a rhizome or tuber, sometimes fibrous. Leaves mostly simple, occasionally palmately lobed or compound, alternate, often in 2 ranks, usually asymmetrical at the base; stipules unequal, large, membranous, often soon shed. Flowers unisexual with free, mostly petal-like segments (in Begonia). Male flowers with (2)4 petal-like segments in two opposite pairs, the stamens are numerous, free or united. Female flowers with 2-5 segments. Carpels 2-3(-6) united. Ovary inferior, usually 3-chambered and with 3 wings; ovules numerous with axile placentation; stigmas usually twisted. Fruit mostly a winged capsule containing numerous seeds.
The family contains only 3 genera: Begonia is well known to horticulture and contains almost all the species; Hillebrandia has a single species, H. sandwicensis that is native to Hawaii; Symbegonia, is endemic to Papua New Guinea and has 12 species.
In the Moluccas leaves of B. tuberosa are eaten as a vegetable, other species are used medicinally.
Plants generally recognised by their ornamental leaves that are divided by the main vein into 2 unequal parts; flowers unisexual, often showy in bright colours; ovary inferior with twisted stigmas; fruit and ovary 3-winged.
3 genera and over 1600 species, subspecies and varieties (with many species still to be described) from tropical and subtropical regions, almost all in the genus Begonia and with a centre of distribution in northern S America.
Source: (1997). Begoniaceae. In: . Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.