Betula bomiensis P.C.Li

Small tree to 8 m with arching branches. Twigs more or less glabrous; young shoots initially densely softly silky hairy, to 2.5 mm in diam., smooth, brown, eglandular, with small (0.5– 1.0 mm) lenticels, white, roundish to elliptic, longitudinally elongated. Buds ovoid, acute, about 6 × 3 mm. Petiole 3–6 mm. Leaf blade from very small to 38 × 30 mm (rarely to 40 × 34 mm), with (5–) 9–13(–15) pairs of veins; veins deeply indented; secondary veins running to the sinus between the teeth and then bending up into the tooth; 1 (rarely 2) teeth between the teeth ending the secondary veins; secondary veins close 2 mm apart (–3 mm towards the apex); weak basal veins usually absent; margin recurved. Male catkins 1, or 2 or 3 in a cluster, to 4.7 cm; bracts densely yellow tomentose. Female catkins initially deflexed, clearly downward pointing, soon becoming erect. Fruiting catkin up to 18(–32) × 9 mm with peduncle about 3.5–8 mm and bracts usually covered with silky hairs. Scales silky hairy on dorsal (abaxial) surface, with ciliate margins, and apical hairs longer and twisted together to make point to 1.5 mm long. Seeds c. 2 × 1–1.5 mm, hairy towards apex; style c. 1 mm. Flowering June; fruiting October. Tetraploid: 2n=56.

Distribution  China southeast Xizang (Tibet), southwest and west Gansu

Habitat Margins of broad-leaved forests at approx. 2400 m asl.

Taxonomic note Flora of China treats Betula bomiensis as a synonym of B. delavayi var. microstachya P.C.Li, described from Sichuan.