Agrostis clavata Trin.

Agrostis clavata is distinguished by the combination of scabrid leaves and panicle branches, small, pale green spikelets, acuminate glumes, an awnless lemma, and very small palea and anthers.

Agrostis clavata subsp. matsumurae (A. clavata var. nukabo) is often recognized, mainly on the basis of a dense, narrow panicle bearing spikelets from the base of the primary branches. In contrast, subsp. clavata has panicle branches divergent at flowering and bare in the lower 1/3–1/2. However, short, densely spiculate branches are often present at the panicle nodes among the longer, bare-based branches in subsp. clavata, contributing to a denser panicle appearance when frequent. All the panicle branches become erect in the fruiting stage, further blurring the boundary with subsp. matsumurae. It has not been possible to distinguish two subspecies satisfactorily in herbarium material.

Tufted annual or perennial, then with a few cataphylls at base, without rhiaome or stolons, branchiing at base, glabrous. Culms up to 60 cm long. Sheaths smooth; uppermost ligules quadrangular, 0.75-2 mm long, apex rounded, reose; bldes erect, flat, up to 18 cm long, 3.5 mm wide, smooth to scaberulous. Panicle contracted, somewhat lobed and rather densely spikeld, 8.5-19 cm long, 1-3 cm wide, branches usually scaberulous, lowermost 2-8 together, longest 4.6-7.5 cm long, the shorter often spikeled nearly to base. Spikelets 1.6-2.25 mm long. Glumes unequal, the lower longest, ovate-lanceolate. Rachilla process absent. Lemma 1.25-1.6(-1.7) mm long, 0.6-0.82 times as long as as the lower glume; acutish, 5-nerved, Trichodium-net well-developed; callus oblique, glabrous or with an occasional up to 0.1 mm long hair; awn absent. Palea 0.2-0.5 mm long, 0.13-0.36 times as long as the lema. Anthers 0.2-0.5(-0.55) mm long, 0.15 times as long as the lemma.

Annual or short-lived perennial, loosely tufted. Culms erect or geniculate at base, slender, 30–70 cm tall, 2–4-noded. Leaf sheaths smooth; leaf blades linear, flat, thin, 6–15 cm × 1–5 mm, both surfaces scabrid; ligule 1.5–3 mm, back scabrid, apex obtuse or lacerate. Panicle lax, lanceolate to narrowly oblong in outline, 8–25 cm; branches 2–7 at each node, ascending, capillary, 8–15 cm, scabrid, bare in lower 1/3–1/2 or sometimes with spikelets from base. Spikelets 1.5–2.5 mm, yellowish green; glumes lanceolate, subequal, lower slightly longer, keeled, keels aculeate-scabrid, apex acuminate; callus glabrous or nearly so; lemma 2/3–3/4 spikelet length, awnless, apex obtuse; palea to 0.25 mm. Anthers 0.3–0.5 mm. Fl. and fr. summer and autumn.

Distributed in N. Europe to Sachalin, Japan, Taiwan.

Anhui, Fujian, Gansu, Guangdong, Guizhou, Hebei, Henan, Heilongjiang, Jilin, Nei Mongol, Shaanxi, Shandong, Sichuan, Taiwan, Xizang, Yunnan [Japan, Korea, Mongolia, Russia; SW Asia (Caucasus), N Europe, North America (Alaska)].

Roadsides, riversides, forest margins, disturbed grassy places, often in moist situations; below 4000 m.

Agrostis matsumurae Hack. ex [Matsjmura, Bot. Mag. Tokyo 11: 445. 1897, nomen] Honda, J. Sc. Imp. Univ. Tokyo 3, 3(1): 191. 1930.
Agrostis clavata Trin. subsp. matsumurae Tateoka, Bull. Nat. Sc. Mus. Tokyo 11: 161. 1968; Hsu, Fl. Taiwan 5: 398. 1978.
Agrostis formosana Ohwi, Bot. Mag. Tokyo 55: 354. 1941.
Agrostis clavata Trin. var. nukabo Ohwi, Bot. Mag. Tokyo 55: 356. 1941.
Agrostis exarata Trin. subsp. clavata (Trin.) Koyama, Grass. Jap. Neighb. Reg. 196. 1987.

Agrostis clavata subsp. matsumurae (Hackel ex Honda) Tateoka; A. clavata var. nukabo Ohwi; A. formosana Ohwi; A. matsumurae Hackel ex Honda.

Annuals, Terrestrial, not aquatic, Stems nodes swollen or brittle, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly basal, below middle of stem, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 2-10 mm wide, Leaf blades mostly flat, Leaf blade margins folded, involute, or conduplicate, Leaf blades mostly glabrous, Ligule present, Ligule an unfringed eciliate membrane, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence branches more than 10 to numerous, Lower panicle branches whorled, Flowers bisexual, Spikelets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating above the glumes, glumes persistent, Spikelets disarticulating beneath or between the florets, Rachilla or pedicel glabrous, Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes equal to or longer than adjacent lemma, Glume equal to or longer than spikelet, Glumes 1 nerved, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma 5-7 nerved, Lemma glabrous, Lemma apex truncate, rounded, or obtuse, Lemma awnless, Lemma mucronate, very shortly beaked or awned, less than 1-2 mm, Lemma margins thin, lying flat, Lemma straight, Palea 2 nerved or 2 keeled, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.