西桦 xi hua

Betula acuminata Wallich; B. alnoides var. acuminata (Wallich) H. Winkler; Betulaster acuminata (Wallich) Spach.

Trees to 30 m tall; bark gray, exfoliating. Branchlets densely white villous and resinous glandular. Petiole 1.5-3(-4) cm, densely villous and glandular punctate; leaf blade lanceolate, ovate-lanceolate, or ovate-elliptic, 4-12 × 2.5-5.5 cm, papery, abaxially densely glandular punctate, sparsely villous along veins, bearded in axils of lateral veins, adaxially glabrous, base cuneate, broadly cuneate, or subrounded, rarely subcordate, margin irregularly incurved setiform serrate, apex acuminate or caudate-acuminate; lateral veins 10-13 on each side of midvein. Female inflorescences 3-5 in a raceme, pendulous, narrowly cylindric, 5-10 cm × 4-6 mm when mature; peduncle 2-3 mm, densely yellow villous; bracts ca. 3 mm, densely pubescent and ciliolate, becoming spongy at base, 3-lobed, middle lobe oblong or obtuse, lateral lobes reduced, auriculate. Nutlet obovate, 1.5-2 mm, sparsely pubescent at apex, with membranous wings ca. 2 × as wide as nutlet. Fl. Oct-Jan, fr. Mar-May. 2n = 28.

Subtropical forests; 700-2100 m. Fujian, Guangxi, Hainan, Hubei, Sichuan, S Yunnan [Bhutan, India, Myanmar, Nepal, Thailand, Vietnam]