蒺藜草 ji li cao

Annual. Culms geniculate, usually rooting at basal nodes, 15–90 cm tall. Leaf sheaths keeled, usually imbricate at base; leaf blades linear or linear-lanceolate, 5–20(–40) × 0.4–1 cm, glabrous to pubescent; ligule ca. 1 mm. Inflorescence 3–10 × ca. 1 cm, burrs contiguous, rachis scabrous. Burrs globose, 0.4–1 cm, truncate, stipe pubescent, all spines and bristles retrorsely barbed; inner spines connate for 1/3–1/2 their length forming a globose cupule, the flattened free tips triangular, erect or bent inward, cupule and tips pubescent, outer spines in 2 divergent whorls, a median whorl of stout rigid spines equaling the inner teeth, and an outermost whorl of relatively few short, slender bristles. Spikelets 2–4 in burr, 4.5–7 mm; lower glume 1/2 spikelet length; upper glume 2/3–3/4 spikelet length. Fl. and fr. summer. 2n = 34, 68.

Seashore sand dunes, roadsides, waste places. Fujian, Guangdong, Hainan, Taiwan, Yunnan [native to America; now a widespread weed of the tropics and subtropics].

The name Cenchrus caliculatus Cavanilles has been misapplied to this species in China. Cenchrus caliculatus is a larger species with culms to 2 m tall and an inflorescence to 24 cm. It is further distinguished by its burrs, which have only a shallow basal cupule. It occurs in Indonesia, Australia, and the S Pacific Islands.