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Poa compressa L.

Common name
Canada Bluegrass

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

compressa- from the Latin comprimo (squeeze together). Culms flattened.

Published in
Sp. Pl. 69 (1753).

Perennial, culms solitary or tufted. Rhizomes elongated. Basal leaf sheaths glabrous. Young shoots extravaginal. Culms erect or geniculately ascending, slender, 10–60 cm tall, wiry, 4–6-noded. Mid-culm internodes elliptical in section, smooth, glabrous. Lateral branches simple or branched. Leaves mostly basal. Leaf-sheaths smooth. Ligule an eciliate membrane or a fringed membrane, 0.4–1.3(–3) mm long, truncate or obtuse. Leaf-blades flat or conduplicate, 2–12 cm long, 1–4 mm wide, rigid or firm. Leaf-blade surface smooth or scaberulous, glabrous. Leaf-blade apex abruptly acute.

Inflorescence compound, a panicle. Panicle open or contracted, oblong or ovate, dense or loose, 1.2–10 cm long, 0.5–3 cm wide. Primary panicle branches ascending, 2–4-nate, bearing spikelets almost to the base. Panicle branches straight, angular, scaberulous.

Spikelets solitary. Pedicels 0.3–2 mm long. Fertile spikelets many flowered, comprising 3–10 fertile florets, with diminished florets at the apex, elliptic or oblong or ovate, laterally compressed, 3–8 mm long, breaking up at maturity. Spikelets disarticulating below each fertile floret. Rhachilla internodes obscured by lemmas, smooth. Floret callus glabrous or woolly.

Glumes persistent, similar. Lower glume ovate, 1.6–3 mm long, 90–100% length of upper glume, membranous, 1-keeled, 3-nerved, midnerve scabrous. Lower glume apex acute. Upper glume ovate, 1.6–3 mm long, 90–100% of length of adjacent fertile lemma, membranous, 1-keeled, 3–5-nerved, midnerve scabrous. Upper glume apex acute.

Fertile lemma oblong, oblong in profile, 2–3 mm long, membranous, much thinner above, 5-nerved. Lemma midnerve ciliate, hairy below. Lemma lateral nerves obscure, stopping well short of apex. Lemma margins ciliate, hairy below. Lemma apex acute. Palea 100% of length of lemma. Palea keels scabrous. Apical sterile florets resembling fertile though underdeveloped. Lodicules 2, membranous. Anthers 3, 1.2–1.9 mm long. Grain with adherent pericarp. Hilum punctiform.

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

Australian Distribution:
New South Wales, Victoria, Tasmania.

New South Wales: Central Coast, Northern Tablelands, Central Tablelands, Southern Tablelands, Central-Western Slopes. Victoria: Eastern Highlands, Gippsland Plains, Wilsons Promontory. Tasmania: West Coast, East Coast.

Classification. (GPWG 2001):
Pooideae: Poeae

Introduced. Widespread, native to Europe. Coloniser of waste lands and disturbed ground, often on shallow well-drained soils, also a weed of pasture.

Illustrations available:
Inflorescence (scanned specimen)
Spikelet (photo)
Australian distribution

Inflorescence (scanned specimen)
© Queensland Herbarium
AQ 293968
by D.Sharp

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Spikelet (photo)
© Queensland Herbarium
AQ 293968
by D.Sharp

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Australian Distribution

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