Poa pusilla

Detailed description

Slender, often delicate, open, perennial tufts, 5 – c. 35 cm, with few, very narrow, flaccid, bright green leaves, and slender, long-creeping rhizome; branching extravaginal; leaf-blades persistent. Leaf-sheath greenish purple becoming light brown, ± membranous, distinctly keeled, ribs strong, whitish, shaggy pubescent-scabrid, or minutely scabrid throughout or only near hyaline margins, occasionally with a few longer hairs on margins near ligule, rarely completely glabrous. Ligule 0.2–0.5 mm, truncate, ciliate, sometimes erose, abaxially with minute hairs. Leaf-blade (1)–5–15–(25) cm × c. 0.5 mm diameter, folded, rarely flat and wider, margins inrolled, abaxially distinctly ribbed, glabrous, adaxially with scattered short hairs especially on midrib, tip subacute to curved, scabrid on midrib. Culm 3–30–(50) cm, very slender, erect or drooping above, internodes glabrous. Panicle 1.5–8.5 cm; branches spreading, few, filiform, scabrid, bearing 1–4 spikelets at tips. Spikelets 3–7.5 mm, 2–5–(7)-flowered, yellow-green, faintly purplish. Glumes subequal, 2–4–(4.5) mm, 3-nerved, narrow elliptic- to ovate-lanceolate, acute or subacute, smooth, midnerve and sometimes lateral nerves sparsely scabrid. Lemma 2–4–(5) mm, 5-nerved, oblong- to ovate-elliptic, obtuse, midnerve with long silky crinkled hairs in lower ½, sometimes scabrid above hairs, lateral nerves usually with conspicuous silky hairs near base or in lower ½, internerves usually smooth, rarely finely scabrid, with hyaline band at slightly erose tip. Palea 2–3.5 mm, keels short ciliate-scabrid, interkeel short pubescent-scabrid, flanks smooth to scabrid. Callus with thick tuft of long, silky crinkled hairs. Rachilla (0.3)–0.6–0.8 mm, with scattered long hairs. Lodicules c. 0.5 mm. Anthers 1–2 mm. Caryopsis c. 1 × 0.5 mm. 2n= 28.