Description from Flora of China
Sambucus barbinervis Nakai; S. buergeriana (Nakai) Blume ex Nakai; S. buergeriana f. cordifoliata Skvortsov & W. Wang; S. foetidissima Nakai; S. junnanica J. J. Vassiljev; S. latipinna Nakai var. pendula Skvortsov; S. manshurica Kitagawa; S. peninsularis Kitagawa; S. potaninii J. J. Vassiljev; S. racemosa Linnaeus subsp. manshurica (Kitagawa) Voroschilov; S. sieboldiana (Miquel) Blume ex Schwerin var. buergeriana Nakai.
Shrubs or small trees, 5-6 m tall. Old branches reddish brown, with conspicuous, narrowly elliptic lenticels; pith brownish. Leaves imparipinnate; leaflets (1 or)2- or 3(-5)-jugate; lateral leaflets ovate-orbicular or narrowly elliptic to oblong-oblanceolate, 5-15 × 1.2-7 cm, base cuneate or rounded, sometimes cordate, asymmetrical, margin irregularly serrate, sometimes with 1 to several glandular teeth at base or below middle, apex acute to acuminate or caudate; lowest pair of leaflets sessile or petiole to ca. 0.5 cm; terminal leaflet ovate or obovate, adaxially sparsely pubescent when young, glabrescent, petiolule ca. 2 cm, base cuneate, apex acuminate or caudate; stipules narrowly linear or reduced to bluish protrusions. Inflorescences terminal cymose panicles, 5-11 × 4-14 cm, pedunculate, sometimes sparsely pubescent, soon glabrescent. Flowers appearing simultaneously with leaves, dense; calyx tube urceolate, ca. 1 mm, lobes triangular-lanceolate, slightly shorter than tube; corolla pinkish in bud, white or yellowish when open; tube short; lobes oblong or narrowly ovate-orbicular, ca. 2 mm; stamens spreading, ca. as long as corolla lobes; filaments slightly dilated at base; anthers yellow; ovary 3-loculed; styles short; stigmas 3-lobed. Fruit red, rarely bluish or purplish black, ovoid or subglobose, 3-5 mm in diam.; pyrenes 2 or 3, ovoid to ellipsoid, 2.5-3.5 mm, slightly rugose. Fl. Apr-May, fr. Sep-Oct. 2n = 36*.
Sambucus williamsii was treated as a synonym of a highly variable, circumboreal S. racemosa Linnaeus by Bolli (Diss. Bot. 223: 187-197. 1994). The black fruit and dark green leaves (Bolli, loc. cit.) distinguish S. williamsii and S. melanocarpa A. Gray of W North America from other members of the S. racemosa complex. Sambucus williamsii also has a more pronounced fetid odor. Because of the high degree of variation and the pronouncement by Bolli (loc. cit.) that the variation within his circumscription of S. racemosa should be further evaluated in a geographic context through field, cytological, and biochemical methods, for the time being, we prefer to maintain S. williamsii, and, with less certainty, the following species, S. sibirica, as distinct.
● Mountain slopes, scrub, streamsides, roadsides, beside houses; 500-1600 m. Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jilin, Liaoning, Shaanxi, Shandong, Shanxi, Sichuan, Yunnan, Zhejiang.