Tetradium ruticarpum

Tetradium ruticarpum (formerly Evodia rutaecarpa), source of the Chinese herb wu zhu yu, is a deciduous shrub or small tree of the citrus family (Rutaceae) reaching about 9 metres tall. The opposite, pinnately compound leaves bear five to eleven ovate to elliptic, aromatic leaflets, downy beneath and dotted with oil glands. In summer it produces large, flattened, terminal clusters of small, greenish-white to yellowish unisexual flowers. The fruit is a small, reddish-purple to dark red dehiscent capsule borne in dense clusters that superficially resemble peppercorns, each splitting to release glossy black seeds; the dried, nearly ripe fruits are strongly aromatic and pungently bitter. Native to warm-temperate and subtropical Asia, particularly China and Korea, it grows in mountain forests and thickets and is widely cultivated in China for medicinal use.