21. Betula platyphylla Sukaczev, Trav. Mus. Bot. Acad. Imp. Sci. St.-Petersbourg. 8: 220. 1911.
白桦 bai hua
Betula alba Linnaeus subsp. latifolia Regel; B. alba subsp. mandshurica Regel; B. alba subsp. tauschii Regel; B. japonica Siebold ex H. Winkler; B. japonica var. mandshurica (Regel) H. Winkler; B. japonica var. rockii Rehder; B. japonica var. szechuanica C. K. Schneider; B. latifolia Komer; B. mandshurica (Regel) Nakai; B. platyphylla var. japonica Hara; B. platyphylla var. mandshurica (Regel) Hara; B. platyphylla var. szechuanica (C. K. Schneider) Rehder; B. szechuanica (C. K. Schneider) Jansen; B. verrucosa Ehrhart var. platyphylla (Sukaczev) Lindley ex Jansson.
Trees to 30 m tall; bark grayish white, exfoliating in sheets. Branches not pendulous, dark gray or dark brown, glabrous; branchlets brown, sparsely resinous glandular. Petiole slender, 1-2.5 cm; leaf blade triangular, ovate-triangular, rhombic-triangular, rhombic-ovate, or broadly ovate, 3-9 × 2-7.5 cm, abaxially densely resinous punctate, glabrous, bearded in axils of lateral veins, adaxially sparsely pubescent and resinous glandular when young, base truncate, broadly cuneate, or cuneate and subcordate, margin doubly or simply serrate, or incised-serrate, apex acute, acuminate, or caudate-acuminate; lateral veins 5-7(-9) on each side of midvein. Female inflorescence pendulous, oblong or oblong-cylindric, 2-5 × 0.6-1.4 cm; peduncle slender, 1-2.5 cm; bracts 5-7 mm, densely pubescent and ciliate, 3-lobed, middle lobe triangular-ovate, lateral lobes erect or spreading to recurved, ovate or suborbicular, slightly shorter to longer than middle lobe. Nutlet narrowly oblong, oblong, or ovate, 1.5-2 × 1-1.5 mm, sparsely pubescent, with membranous wings slightly longer than and about as wide as nutlet. Fl. Jun-Jul, fr. Jul-Sep. 2n = 28.
Temperate broad-leaved forests, shaded, S-facing slopes, ridges, dry, sunny slopes, marshes, forming vast, pure stands or mixed with Acer, Larix, Picea, Tilia, and other species of Betula; 700-4200 m. Gansu, Hebei, Heilongjiang, Henan, Jiangsu, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shanxi, SW and W Sichuan, SE Xizang, NW Yunnan [Japan, N Korea, E Mongolia, Russia (Far East, Siberia)]
This species has been divided into varieties or separate species (B. japonica, B. mandshurica, and B. szechuanica); however, the morphological characters are not distinct; therefore, the entities are all treated here as B. platyphylla. A. K. Skvortsov considers B. platyphylla to be synonymous with B. pendula.
A very important timber tree. The wood is soft and light, close grained, and fine to coarse textured; it is used for making agricultural tools, wooden ware, and tobacco boxes, and rarely
for house construction. The white, papery bark is made into canoes and fancy articles, food baskets, and is also used as a substitute for tiles; the inner bark contains much resin.