Derivation
Poa L., Sp. Pl. 67 (1753); from the Greek poa (grass, especially as fodder).

infirma- from the Latin for lax or weak. Culms decumbent.

Published in
F.W.H.A. von Humboldt et al., Nov. Gen. Sp. 1: 158 (1816).

Habit
Annual, tufted. Basal leaf sheaths herbaceous. Young shoots intravaginal. Culms erect or geniculately ascending or decumbent, 1–25 cm tall, 1–3-noded. Mid-culm internodes terete, smooth. Lateral branches simple or sparsely branched. Leaves mostly basal. Leaf-sheaths smooth. Ligule an eciliate membrane, 0.9–3 mm long, obtuse or acute. Leaf-blades flat or conduplicate, (0.5–)2–5.5(–8) cm long, 0.9–4 mm wide. Leaf-blade surface smooth, glabrous. Leaf-blade margins scaberulous. Leaf-blade apex obtuse or abruptly acute, hooded.

Inflorescence
Inflorescence compound, a panicle. Panicle open or contracted, lanceolate or ovate, dense or loose, 0.5–10 cm long. Primary panicle branches spreading, 1–2-nate. Panicle branches smooth.

Spikelets
Spikelets solitary. Pedicels 0.3–3 mm long. Fertile spikelets many flowered, comprising 2–4 fertile florets, with diminished florets at the apex, oblong or ovate, laterally compressed, 2–4 mm long, breaking up at maturity. Spikelets disarticulating below each fertile floret. Rhachilla internodes eventually visible between lemmas, smooth. Floret callus pubescent.

Glumes
Glumes persistent, similar. Lower glume ovate, 0.9–1.5 mm long, 60–70% length of upper glume, membranous, 1-keeled, 1–3-nerved. Lower glume lateral nerves absent. Lower glume apex acute. Upper glume elliptic or oblong, 1.3–2.5 mm long, 90–100% of length of adjacent fertile lemma, membranous, 1-keeled, 1–3-nerved. Upper glume apex obtuse.

Florets
Fertile lemma ovate, oblong in profile, 1.8–2.5 mm long, membranous, much thinner above, much thinner on margins, 5-nerved. Lemma lateral nerves stopping well short of apex. Lemma surface pubescent, hairy on nerves. Lemma apex obtuse. Palea 100% of length of lemma. Palea keels ciliate. Apical sterile florets resembling fertile though underdeveloped. Lodicules 2, membranous. Anthers 3, 0.2–0.5 mm long. Grain with adherent pericarp. Hilum punctiform.

Continental Distribution:
Europe, Africa, Temperate Asia, Tropical Asia, Australasia, South America, Antarctica.

Australian Distribution:
Western Australia, South Australia, New South Wales, Victoria, Tasmania.

Western Australia: Roe, Avon. South Australia: Eyre Peninsula, South-eastern. New South Wales: Northern Tablelands, Central Tablelands, Southern Tablelands, North-Western Plains. Victoria: Murray Mallee, Midlands, Otway Plain, Gippsland Plains, Wilsons Promontory. Tasmania: North East, East Coast.

Classification. (GPWG 2001):
Pooideae: Poeae

Notes
Introduced. Native to Europe, now widely naturalised. Occasional but widespread. Flowers Aug.–Nov. Fruits Sept.–Nov.