Clethra barbinervis Siebold & Zucc.

Trees or shrubs, 1–9 m tall, deciduous. Petiole 0.6–2.4 cm; leaf blade ovate, lanceolate-ovate, elliptic, oblanceolate, or obovate, 5.2–11 × 2.8–4.8 cm, papery, abaxially appressed pilose or glabrous on major veins and often stellate-tufted in secondary vein axils, glabrous elsewhere, and reticulations dark brown but not raised, base attenuate to cuneate or occasionally obtuse to subrounded, margin sharply serrate nearly throughout or basal 1/4–1/3 entire, teeth 22–39 per side on larger leaves and 1–4 mm apart, apex acuminate; secondary veins (8–)11–14 on each side of midvein. Racemes or raceme branches (1–)3–8 per twig, 5–17 cm, grayish brown or brown stellate-tomentose but sometimes sparsely so, thickest rachis on each twig basally 0.8–1.7 mm in diam.; bracts linear-subulate, 3–6 mm. Pedicel 1.5–5.5 mm at anthesis. Sepals ovate, 2–3(–3.8) × 1.2–1.6 mm, outside densely white stellate-tomentose and surface (visible through pubescence) usually medially blackened, midvein usually indistinct at anthesis, apex obtuse. Petals white, 3–4 × 2–2.9 cm, outside smooth, inside glabrous, margin thickened and apically fimbriate. Stamens 4–5.3 mm, exserted; filaments glabrous or occasionally sparsely pilose; anthers 1.3–2 mm. Style 1.5–3.5 mm at anthesis, glabrous, apex 3-lobed to shallowly 3-cleft. Fruiting pedicel 4–9 mm. Ovary and capsule apically hirsute with longer hairs 0.7–1.1 mm; persistent style 3–5 mm. Fl. Jun–Aug, fr. Sep–Nov. 2n = 32.

Anhui, Fujian, Hubei, Hunan, Jiangxi, Shandong (Lao Shan), Zhejiang [Japan, Korea].

Open deciduous montane forests, ± dry places; 800–1800 m.

Clethra barbinervis, the Japanese clethra, is a species of flowering plant in the family Clethraceae. It is native to eastern Asia, where it is found in southern China, Korea, and Japan. Its natural habitat is in open mountain forests. It is a common species in Japan, and is often found in disturbed secondary forests.

It is an upright shrub growing to 3 m (9.8 ft). Its leaves are deciduous, dark green, and are 5 cm (2 in) long. Racemes of small, fragrant, white flowers 15 cm (6 in) long are produced in late summer and autumn. Mature specimens have peeling bark. The bark is plain, blackish brown with twigs turning back.

This plant has gained the Royal Horticultural Society's Award of Garden Merit. Though hardy in cultivation, it requires a sheltered location in temperate regions.

Detail of leaves and flowers