Arundinella hirta (Thunb.) Tanaka

This polymorphic species exhibits much minor variation in the hairiness of culms, nodes, and leaves, and many infraspecific names have been applied. The name Arundinella anomala has been used in the past for plants with glabrous culms and glabrous to moderately hairy leaf sheaths, whereas plants with densely hairy culms and leaf sheaths have been referred to A. hirta. However, the protologue of A. hirta states that the culms are glabrous. In practice, the different combinations of hairiness of culms, nodes, and leaves make a subdivision into two entities impracticable on this character, even at infraspecific rank. Rarely variants occur with setose spikelets, and these can be recognized at varietal rank.

Poa hirta Thunb., Fl. Jap. 49. 1784. Rhizome well developed, creeping, densely covered with scaly leaves; culms erect, hard, 2-4 mm in diameter. Blades 12-25 cm long by 4-12 mm wide; more or less scabrid hairy; sheath at least tubercle-hairy along margin; ligule short, membranous. Panicle 8-25 cm long, more or less scabrid bristled on the main axis, branches up to 10 cm long; the branches and pedicels scabrid. Spikelets ovate-lanceolate, 3-5 mm long; glumes lanceolate, nerves prominent, 3-5, scabrous along elevated nerves; lower glume 1/2-2/3 as long as the spikelet, with an internode between the glumes; upper glume nearly as long as the spikelet, 5-nerved; lower lemma awnless, 3-5-nerved, nearly as long as the glume; lower palea slightly shorter, staminate; anthers about 2.5 mm long; upper lemma 2-3.5 mm long, mucronate; callus hairy, the hairs about 1/2 as long as the upper lemma.

Perennial, loosely tufted with stout scaly rhizomes. Culms erect, 60–150 cm tall, 2–5 mm in diam., glabrous or less often tuberculate-hispid or densely pilose, nodes glabrous or bearded. Leaf sheaths usually tuberculate-hispid on margins, often thinly hispid throughout, less often densely pilose or completely glabrous; leaf blades broadly linear, 10–50 cm × (4–)7–15 mm, tuberculate-setose on margins only, or thinly hispid to densely pilose on both surfaces, or glabrous, apex long-acuminate; ligule 0.2–0.7 mm. Panicle contracted, narrowly elliptic-oblong in outline, 8–45 cm; central axis scabrid to setose; branches 5–20 cm, ascending, lower often with branchlets, densely spiculate; pedicels scabrid. Spikelets 3–4.8 mm, plump; glumes glabrous or rarely hispid, scabrid along prominent veins; lower glume 2.5–4 mm, 3(–5)-veined; upper glume 5–7-veined; lower floret subequal to spikelet; upper floret 2.5–3.5 mm, lemma apex acute to shortly mucronate, callus hairs nearly 1/2 length of lemma. Fl. and fr. Jul–Oct. 2n = 28, 34, 36, 56.

Distributed in Japan, Korea and China.

Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Ningxia, Shaanxi, Shandong, Sichuan, Taiwan, Yunnan, Zhejiang [Japan, Korea, E Russia].

Grassy mountain slopes, river banks, roadsides, field margins; 100–1500 m.