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Perennials, strongly rhizomatous, shoots extravaginal. Culms wiry, compressed, erect, often geniculate at base, simple or sparsely tufted, 15–50(–60) cm tall, 1.5–2 mm wide, nodes compressed, 3–6, 2–5 exserted. Leaf sheaths compressed to keeled, smooth, uppermost closed for 1/10–1/5 of length; blades flat, 5–12 cm × 1.4–4 mm, surfaces smooth or adaxially scabrid; ligule 1–3 mm, abaxially scabrid, truncate to obtuse. Panicle contracted or slightly open, erect, narrow, 4–11 × 0.5–1(–3) cm; branches erect or steeply ascending, or eventually spreading, 1–3 per node, densely scabrid angled from base, longest 2–4 cm with spikelets moderately crowded from the base or in distal 2/3. Spikelets ovate-lanceolate, 3.5–5 mm, florets 2–4; glumes lanceolate, nearly equal, 2–3 mm, 3-veined, apex acute or thinly mucronate, keel scabrid, rachilla smooth or minutely bumpy; lemmas oblong, 2.3–3.5 mm, apex obtuse, keel shortly villous for 2/3 of length, marginal veins to 1/3, intermediate veins faint, areas between veins glabrous; callus sparsely webbed or glabrous; palea keels scabrid. Anthers 1.3–1.8 mm. Fl. and fr. Jun–Aug. 2n = 14, 35, 42, 45, 49, 50, 56, 59.
Perennial, usually spreading by wiry rhizomes, sometimes weakly caespitose. Culms 10–26 (–60) cm high; mid-culm internodes glabrous, compressed. Young shoots extravaginal. Leaves: basal sheaths with margins connate toward base, glabrous, sometimes purplish; ligule 0.4–1.3 (–3) mm long, obtuse to truncate, apically glabrous or minutely ciliolate, abaxially scabridulous or sparsely hairy; blade flat or folded, 2–7.5 (–12) cm long, 1.3–2.6 (–4) mm wide, rather stiff with a firm, narrowly boat-shaped apex, adaxially glabrous, abaxially glabrous or occasionally scabrous near apex. Panicles contracted, 1.2–8.5 cm long. Spikelets 3.4–6.4 (–8) mm long, with 3–8 (–10) bisexual florets. Glumes with lateral nerves often obscure; lower glume 1.6–2.3 mm long, 3-nerved; upper glume 1.6–2.6 mm long, 3–5-nerved. Web absent to well-developed. Lemma 2–3 mm long, 5-nerved, with lateral nerves often obscure; keel villous in lower half, scabrous or glabrous above; marginal nerves with hairs towards base or glabrous; intercostal regions glabrous. Anthers 1.2–1.9 mm long.
Culms erect, 2–7 dm from long running rhizomes, not tufted, strongly flattened, 2-edged; lvs 2–4 mm wide, the cauline ones seldom over 1 dm; ligule short, mostly 1–2 mm; infl usually compact and narrow, bluish-or grayish-green, 2–8 cm, its branches usually paired, bearing spikelets to near the base; pedicels of the lateral spikelets 0.5 mm; spikelets 4–6 mm, 3–6-fld; first glume 1.7–2.4 mm, the second 1.8–2.8 mm; lemmas firm, 2–2.8 mm, with or without a small basal web, slightly pubescent on the keel and marginal veins below, the intermediate veins obscure; anthers 0.9–1.7 mm; 2n=14–56. Native of Europe, established in open, usually dry, variously acid or (along highways) alkaline soil throughout our range, to Alas., Ga., and the Pacific.
