11. Paspalum scrobiculatum Linnaeus, Mant. Pl. 1: 29. 1767.
鸭毑草 ya jie cao
Perennial or annual. Culms tufted, slender to robust, erect or decumbent and rooting at lower nodes, 30–90(–150) cm tall. Leaf sheaths compressed, keeled, usually glabrous; leaf blades linear or linear-lanceolate, 10–40 × 0.4–1.2 cm, usually glabrous, base subrounded, margins scabrous, apex acuminate; ligule 0.5–1 mm. Inflorescence of 2–5(–8) racemes, subdigitate or on a short axis; racemes 3–10 cm, ascending to widely spreading; spikelets usually single, overlapping in 2 rows, sometimes paired especially in middle of raceme; rachis ribbonlike, 1.5–3 mm wide, margins scabrous. Spikelets green becoming brown, suborbicular, ovate or broadly elliptic, 2–3 mm, glabrous, obtuse to apiculate; upper glume membranous, 3–7-veined; lower lemma membranous or sometimes indurate, 3–5(–7)-veined; upper lemma brown at maturity, subequaling spikelet, coriaceous, finely striate, obtuse. Fl. and fr. May–Nov. 2n = 20, 40 or 60.
Roadsides, weedy places, often on damp soils. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Jiangsu, Jiangxi, Sichuan, Taiwan, Yunnan, Zhejiang [tropics and subtropics of the Old World; introduced in America].
This polymorphic species complex is thought to comprise an apomictic swarm. Some of its components have been described as separate species, but variation is continuous throughout. Robust forms are sometimes separated as Paspalum auriculatum J. Presl & C. Presl. Three recognizable entities are maintained here at varietal rank.