Description from Flora of China
Trees to 7 m tall; bark dark yellow-brown. Branchlets purplish brown, densely white villous and resinous glandular. Petiole 1-1.5 cm, sparsely villous and resinous punctate; leaf blade oblong or ovate-lanceolate, 8-13 × 5-7.5 cm, abaxially densely resinous punctate and villous along veins, bearded in axils of lateral veins, adaxially sparsely villous when young, becoming villous and resinous punctate along midvein, base rounded, rarely subcordate or broadly cuneate, margin irregularly mucronate serrate or setiform serrate, apex acuminate; lateral veins 11-15 on each side of midvein. Female inflorescences 2, sometimes 3 in a raceme, narrowly cylindric, ca. 10 cm × 8 mm when mature; peduncle 0.5-1.5 cm, densely pubescent; bracts rhombic, 4-5 × ca. 3 mm, glabrous, ciliolate along margin, 3-lobed, middle lobe rhombic, lateral lobes triangular, small, ca. 1/2 as long as middle lobe. Nutlet oblong, 3-5 × 1.5-3 mm, sparsely pubescent, with membranous wings ca. 2 × as wide as nutlet. Fl. May-Jun, fr. Jul-Aug.
An endangered species. A. K. Skvortsov indicates that Betula rhombibracteata is very similar to B. cylindrostachya, and further studies may show that they are conspecific.
* Broad-leaved forests; 2500-2800 m. NW Yunnan (Dêqên Xian, Weixi Xian)