《中国植物志》|| 桦木科 BETULACEAE ||桤木组 Sect. 1. Alnus ||日本桤木 Alnus japonica (Thunb.) Steud.

3.日本桤木　赤杨（中国树木分类学），水柯子（台湾）
Alnus japonica (Thunb.) Steud. Nomemcl. Bot. ed. 2. 55. 1840; Sieb. et. Zucc. in Abh. Nath.-Phys. C1. Akad. Wiss. Munch. 4 (3): 230. 1846; Kom. in Acta Horti Petrop. 22: 60. 1903. et фл. CCCP 5: 311. Tабл. 16. pис. 3. 1936; Callier ex　Schneid., Ill. Handb. Laubholzk. 1: 126. fig. 67 h-h. 69 f-g. 1904; Schneid. in Sarg., Pl. Wils. 2: 493. 1916; H. Winkl. in Engler, Pflanzenreich 19 (IV-61): 114. 1916. p. p. excl. syn. var. formosana; Rehd., Man. Cult. Trees and Shrubs 148. 1927;陈嵘, 中国树木分类学158.图112. 1937; 胡先骕, 中国森林树木图志2: 51.图版19. 1948;刘慎谔, 东北木本植物图志206.图版. 75. 图112. 图版76. 2. 图1-4. 1955; Li Hui-tin, Woody Flora of Taiwan 80. fig. 24. 1963. p. p. excl. syn. A. formosana. et A. henryi.; Ohwi, Fl. Jap. 376. 1965. ——Betula japonica Thunb. in Nov. Act. Soc. Sci. Upsal. 6: 45. t. 4. 1799. ——Alnus maritima (Marsh.) Nutt. var. japonica Regel in Bull. Soc. Nat. Moscou 38 (2): 428. 1865. ——Alnus maritima (Marsh.) Nutt. var. arguta Regel. l. c. ——Alnus japonica var. genuina Callier in Fedde, Repert. Spec. Nov. 10: 228. 1911.——Alnus japonica (Marsh.) Nutt. var. latifolia Cal lier, l. c. ——Alnus reginosa Nakai in Bot, Mag. Tokyo 29: 46. 1915.
乔木，一般高6-15米，较少高达20米；树皮灰褐色，平滑；枝条暗灰色或灰褐色，无 毛，具棱；小枝褐色，无毛或被黄色短柔毛，有时密生腺点；芽具柄，芽鳞2枚，光滑。短枝上的叶倒卵形或长倒卵形，长4-6厘米，宽2.5-3厘米，顶端骤尖、锐尖或渐尖，基部楔形，很少微圆，边缘具疏细齿；长枝上的叶披针形，较少与短枝上的叶同形，较大，长可达15厘米，上面无毛，下面于幼时疏被短柔毛或无毛，脉腋间具簇生的髯毛，有时具腺点，侧脉7-11对；叶柄长1-3厘米，疏生腺点，幼时疏被短柔毛，后渐无毛。雄花序2-5枚排成总状，下垂，春季先叶开放。果序矩圆形，长约2厘米，直径1-1.5厘米，2-9枚呈总状或圆锥状排列；序梗粗仕，长约10毫米；果苞木质，长3-5毫米，基部楔形，顶端圆，具5枚小裂片。小坚果卵形或倒卵形，长3-4毫米，宽2-2.5毫米；果翅厚纸质，极狭，宽及果的1/4。
产于吉林、辽宁、河北、山东。生于山坡林中、河边、路旁。江苏北部有栽培。苏联远 东地区、日本、朝鲜也有。模式标本采自日本。
生长迅速，可作造林树种。

《Flora of China》|| Betulaceae || Alnus ||日本桤木 Alnus japonica

9. Alnus japonica (Thunberg) Steudel, Nomencl. Bot., ed. 2. 1: 55. 1840.

日本桤木 ri ben qi mu

Betula japonica Thunberg, Nov. Act. Soc. Sci. Upsal. 6: 45. 1799; Alnus japonica var. latifolia Callier; A. maritima (Marshall) Nuttall var. arguta Regel; A. maritima var. japonica Regel; A. reginosa Nakai.

Trees to 20 m tall; bark gray-brown, smooth. Branches dark gray or gray-brown, striate, glabrous; branchlets brown, glabrous or yellow pubescent when young, sometimes resinous glandular. Buds stipitate, with 2 glabrous, ribbed scales. Petiole 1-3 cm, sparsely resinous glandular and pubescent; leaf blade obovate or obovate-elliptic on dwarf shoots, obovate-lanceolate on branchlets, 4-14 × 2.5-4 cm, abaxially sparsely pubescent at first, glabrescent, sometimes resinous glandular and bearded in axils of lateral veins, adaxially glabrous, base cuneate, margin remotely minutely serrate, apex mucronate, acute, or acuminate; lateral veins 7-11 on each side of midvein. Female inflorescences 2-5 in a raceme, ellipsoid, ca. 2 × 1-1.5 cm; peduncle robust, ca. 1 cm; bracts 3-5 mm, woody, base cuneate, apex rounded, 5-lobed. Nutlet obovate, 2-3 mm, with papery wings ca. 1/4 as wide as nutlet. Fl. May-Jul, fr. Jul-Aug.

Temperate forests, streambanks, roadsides; 800-1500 m. Anhui, Hebei, Henan, Jiangsu, Jilin, Liaoning, Shandong, Taiwan [Japan (including Ryukyu Islands), Korea, Russia (Far East)]