Description from Flora of China
Rumex longisetus A. Baranov & B. Skvortzov.
Herbs annual, rarely biennial, especially in S regions. Stems erect, 15-60 cm tall, branched below middle, grooved, glabrous or weakly shortly papillose. Lower leaves: petiole 1-2.5 cm; leaf blade lanceolate or lanceolate-oblong, 4-15(-20) × 1-3(-4) cm, both surfaces glabrous or shortly papillose below, base narrowly cuneate, margin entire and smooth, or occasionally slightly undulate, apex acute, cauline leaves shortly petiolate or nearly sessile, smaller than basal ones; ocrea fugacious, membranous. Inflorescence paniculate. Flowers bisexual. Pedicel filiform, articulate at base or slightly above base, articulation indistinctly swollen. Outer tepals elliptic, ca. 2 mm; inner tepals enlarged in fruit; valves narrowly triangular-ovate, 2.5-3.5 × 0.8-1.5 mm wide, all valves with tubercles, base truncate, each margin with 2 or 3(or 4) teeth, apex acute; teeth 2.5-3 mm, narrow; tubercles oblong, ca. 1.5 mm. Achenes yellow-brown, shiny, ellipsoid, sharply trigonous, 1.5-2 mm. Fl. May-Jun, fr. Jun-Jul. 2n = 40.
Rumex maritimus s.str. is native to Asia and Europe, but it is nearly absent from E Asia, where it is substituted by closely related and/or similar species. Previous records of R. maritimus from North America (except several localities of introduced plants) were also mainly based on misidentifications of related taxa (mostly R. persicarioides Linnaeus and R. fueginus Philippi). Because of that, earlier literature records of R. maritimus should be critically verified. Distribution patterns of R. maritimus and similar taxa (see below) in China need clarification.
Field margins, riverbanks, streamsides; sea level to 1800 m. ?Fujian, ?Guangxi, ?Guizhou, ?Hainan, Hebei, Heilongjiang, Henan, ?Hubei, ?Jiangsu, Jilin, Liaoning, Nei Mongol, Shaanxi, ?Shandong, Shanxi, ?Taiwan, Xinjiang [Kazakhstan, Mongolia, Myanmar, Russia (Far East, Siberia); Europe; introduced in North America].