天山桦 tian shan hua

Betula alba Linnaeus subsp. soongarica var. microphylla Regel; B. jarmolenkoana Goloskokov.

Trees to 12 m tall; bark yellow-white or yellow-brown, exfoliating in flakes. Branches gray-brown or dark brown, glabrous; branchlets densely pubescent and villous, sparsely resinous glandular. Petiole 5-7 mm; leaf blade broadly ovate-rhombic or ovate-rhombic, rarely ovate or rhombic, 2-7 × 1-6 cm, both surfaces sparsely resinous punctate and villous when young, base broadly cuneate or cuneate, margin doubly and coarsely mucronate serrate, apex acute or acuminate; lateral veins 4-7 on each side of midvein. Female inflorescence oblong-cylindric, 1-4 cm × 5-10 mm; peduncle pendulous, 0.5-1.7 cm, densely pubescent; bracts 5-8 mm, pubescent, ciliate, 3-lobed, middle lobe triangular or oblong, lateral lobes slightly spreading to horizontal or recurved, ovate, oblong, or subrhombic, slightly wider and shorter than middle lobe. Nutlet obovate, ca. 2.5 mm, with membranous wings ca. as wide as or slightly wider and longer than nutlet. Fl. Jun-Jul, fr. Jul-Aug.

Temperate broad-leaved forests, streambanks, valleys, shaded or rocky slopes; 1300-2500 m. Xinjiang (Tian Shan) [Kyrgyzstan, Tajikistan]