They are slow-growing evergreen shrubs and small trees, growing to 2–12 m (rarely 15 m) tall. The leaves are opposite, rounded to lanceolate, and leathery; they are small in most species, typically 1.5–5 cm long and 0.3–2.5 cm broad, but up to 11 cm long and 5 cm broad in "B. macrocarpa". The flowers are small and yellow-green, monoecious with both sexes present on a plant. The fruit is a small capsule 0.5–1.5 cm long (to 3 cm in "B. macrocarpa"), containing several small seeds.