杜仲 du zhong

Trees to 20 m tall. Trunk to 50 cm d.b.h.; bark gray-brown, scabrous. Young branches yellow-brown pubescent at first, soon glabrate, old ones conspicuously lenticellate. Buds shiny red-brown; scales 6–8, margin puberulous. Petiole 1–2.5 cm, sparsely villous; leaf blade pale green adaxially when old, 5–15 × 2.5–7 cm, brown pubescent at first, later pubescent only along veins, lateral veins 6–9-paired, together with reticulate veins slightly prominent abaxially, concave adaxially. Male flowers: stamens ca. 1 cm, glabrous, filaments ca. 1 mm. Female flower: ovary ca. 1 cm, glabrous. Samara 2.5–3.5 × 1–1.3 cm; stipe 2–5 mm, articulate at 1–3 mm pedicel. Seed 1.3–1.5 cm × ca. 3 mm. Fl. Mar–May, fr. Jun–Nov.

Mixed forests, sparse forests, thickets, lower mountains, ridges, valleys, dry ravines, fields, also widely cultivated and locally becoming naturalized; 100--2000 m. Gansu, Guizhou, Henan, Hubei, Hunan, Shaanxi, Sichuan, Yunnan, Zhejiang; cultivated in Anhui and Beijing.

Eucommia ulmoides is a rare species in the wild in China, although it is much cultivated. The timber is used for furniture and fuel; the bark, which contains aucubin, is used medicinally as an invigorator, a tonic for arthritis, and for reducing blood pressure; and the solidified latex is used for lining pipes, insulating electric cables, and for filling teeth.