Poa annua

HABIT Annual, or perennial; short-lived; caespitose. Stolons absent, or present. Butt sheaths herbaceous. Culms erect, or geniculately ascending, or decumbent; 3–30 cm long; 2–4 -noded. Culm-internodes terete; smooth. Lateral branches lacking, or sparse. Leaves mostly basal. Leaf-sheaths keeled; smooth. Ligule an eciliate membrane; 2–5 mm long; obtuse. Leaf-blades flat, or conduplicate; 1–14 cm long; 1–5 mm wide. Leaf-blade surface smooth; glabrous. Leaf-blade margins scaberulous. Leaf-blade apex obtuse, or abruptly acute; hooded.

INFLORESCENCE Inflorescence a panicle.

Panicle open; pyramidal, or ovate; 1–12 cm long. Primary panicle branches spreading; 1–2 -nate. Panicle branches smooth.

Spikelets solitary. Fertile spikelets pedicelled. Pedicels 0.3–4 mm long.

FERTILE SPIKELETS Spikelets comprising 3–10 fertile florets; with diminished florets at the apex. Spikelets oblong, or ovate; laterally compressed; 3–10 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes obscured by lemmas; smooth. Floret callus glabrous, or pubescent.

GLUMES Glumes persistent; similar; shorter than spikelet. Lower glume lanceolate, or ovate; 1.5–3 mm long; 0.7–0.8 length of upper glume; membranous; 1-keeled; 1 -veined. Lower glume lateral veins absent. Lower glume apex acute. Upper glume elliptic, or oblong; 2–4 mm long; 0.9–1 length of adjacent fertile lemma; membranous; 1-keeled; 3 -veined. Upper glume apex acute.

FLORETS Fertile lemma ovate; elliptic in profile; 2.5–4 mm long; membranous; much thinner above; much thinner on margins; keeled; 5 -veined. Lemma lateral veins stopping well short of apex. Lemma surface scaberulous; glabrous, or pubescent; hairy below; hairy on veins. Lemma apex acute. Palea 0.9 length of lemma. Palea keels eciliate, or woolly; adorned all along. Apical sterile florets resembling fertile though underdeveloped.

FLOWER Lodicules 2; membranous. Anthers 3; 0.7–1.3 mm long.

FRUIT Caryopsis with adherent pericarp. Hilum punctiform.

DISTRIBUTION Europe: northern, central, southwestern, southeastern, and eastern. Africa: north, Macaronesia, west-central tropical, northeast tropical, east tropical, southern tropical, south, middle Atlantic ocean, and western Indian ocean. Asia-temperate: Siberia, Soviet far east, Soviet Middle Asia, Caucasus, western Asia, Arabia, China, Mongolia, and eastern Asia. Asia-tropical: India, Indo-China, Malesia, and Papuasia. Australasia: Australia and New Zealand. Pacific: southwestern, south-central, and north-central. North America: Subarctic, western Canada, eastern Canada, northwest USA, north-central USA, northeast USA, southwest USA, south-central USA, southeast USA, and Mexico. South America: Mesoamericana, Caribbean, northern South America, western South America, Brazil, and southern South America. Antarctic: Subantarctic islands.

NOTES Poeae. CEH.

Please cite this publication as detailed in How to Cite Version: 3rd February 2016.