Tropical Signalgrass

This species is a troublesome weed.

Culms slender, straggling or suberect, often spreading, rooting at lower nodes, nodes pubescent. Blades 3-15 cm long, 4-8 mm wide, glabrous or sparsely pilose, margins scabrous; sheath usually shorter than internode and more or less ciliate on margins; ligule a row of hairs, 1-2 mm long. Racemes 3-6, spreading, rather distant along glabrous or sparsely hairy axis; rachis flattened, glabrous or sometimes with scattered stiff hairs. Spikelets solitary, elliptic, 3.1-4.3 mm long, gglabrous; glumes 5-7- veined; lower lemma faintly 5-veined; anther ca. 1.2 mm long.

Annual or short-lived perennial. Culms slender, straggling, rooting at lower nodes, 20–60 cm tall, nodes pubescent. Leaf sheaths loose, glabrous or with tubercle-based hairs or ciliate margins; leaf blades lanceolate or linear-lanceolate, 4–15 × 0.4–1 cm, glabrous or pubescent, base subrounded, margins thicker and scabrous, apex acute or acuminate. Inflorescence axis 3–10 cm; racemes 3–6, 2–4 cm, divergent to reflexed; rachis flat, 0.7–1 mm wide, narrowly winged, nearly glabrous; spikelets single, in 2 rows; pedicels glabrous. Spikelets elliptic to narowly obovate, (3–)3.5–4 mm, glabrous, acute; lower glume broadly ovate, 1/3–1/2 spikelet length, 5–7-veined; upper glume separated from lower glume by a short internode, 5–7-veined; upper lemma finely rugose, apex subacute. Fl. and fr. Sep–Nov. 2n = 72.

Tropics of Old World, introduced in New World.

200-900 m

Hill slopes, grassy places, fields, open forests. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hunan, Jiangxi, Taiwan, Yunnan [tropical Asia, Australia, Pacific Islands].

Panicum subquadripara Trin., Gram. Panic. 145. 1826. Urochloa subquadripara (Trin.) R. D. Webster, Austral. Paniceae 252. 1987; Veldkamp, Blumea 41: 429. 1996.