Shrubs or trees to 10 m tall; bark dull brown or nearly black. Branchlets brown or grayish green-brown, sparsely to densely pubescent or glabrescent; 2-year-old branchlets glaucous. Buds brown, angled, glabrous, apex acute. Stipules obliquely broadly ovate or ovate-lanceolate, on shoots reniform to ovate, with conspicuous teeth, adaxially with small, yellow warts; petiole 5-6(-10) mm, often glandular distally; leaf blade broadly oblong-lanceolate or lanceolate to oblanceolate, 7-10 × 1.5-3 cm, abaxially glaucous or not, pubescent when young, glabrous when mature, adaxially dull green, shiny, base rounded or cuneate, margin glandular serrate, apex usually apiculate. Shoots with leaf blade lanceolate, ca. 15 × 2 cm, apex long acuminate. Male catkin 3(-5) cm; peduncle with 2 or 3 serrate or entire leaflets; bracts yellowish green, oblong or ovate, 1.5-3 mm, both surfaces sparsely pubescent or abaxially subglabrous. Male flower: adaxial and abaxial glands 2- or 4- or 5-lobed; stamens (2 or)3(-5), pubescent at base. Female catkin ca. 3.5(-6) cm; bracts as in male catkin, ca. 1/2 as long as ovary. Female flower: abaxial gland generally smaller than adaxial gland, shorter than stipe; ovary ovoid-conical, 4-5 mm, glabrous; stipe 1-2 mm; style short; stigma 2-lobed. Fl. Apr, fr. May. 2n = 38.

Chinese records of the Asian and European species Salix triandra Linnaeus are referable to S. nipponica.

Along rivers or streams in forest regions; near sea level to 500 m. Hebei, Heilongjiang, Hunan, Jiangsu, Jilin, Liaoning, E Nei Mongol, Shandong, Xizang, Zhejiang [Japan, Korea, Mongolia, Russia (Far East)]