Poa compressa

HABIT Perennial; culms solitary, or caespitose. Rhizomes elongated. Culms erect, or geniculately ascending; 10–60 cm long; wiry; 4–6 -noded. Culm-internodes elliptical in section; smooth. Lateral branches lacking. Leaf-sheaths keeled; smooth. Ligule an eciliate membrane; 0.5–3 mm long; obtuse. Leaf-blades flat, or conduplicate; 2–12 cm long; 1–4 mm wide; stiff. Leaf-blade surface smooth, or scaberulous; glabrous. Leaf-blade apex abruptly acute.

INFLORESCENCE Inflorescence a panicle.

Panicle open, or contracted; oblong, or ovate; dense, or loose; 1.5–10 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. Fertile spikelets pedicelled. Pedicels 0.3–2 mm long.

FERTILE SPIKELETS Spikelets comprising 3–10 fertile florets; with diminished florets at the apex. Spikelets elliptic, or oblong, or ovate; laterally compressed; 3–8 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes obscured by lemmas; smooth. Floret callus woolly.

GLUMES Glumes persistent; similar; shorter than spikelet. Lower glume ovate; 2–3 mm long; 0.9–1 length of upper glume; membranous; 1-keeled; 3 -veined. Lower glume primary vein scabrous. Lower glume apex acute. Upper glume ovate; 2–3 mm long; 0.9–1 length of adjacent fertile lemma; membranous; 1-keeled; 3 -veined. Upper glume primary vein scabrous. Upper glume apex acute.

FLORETS Fertile lemma oblong; elliptic in profile; 2.5–3 mm long; membranous; much thinner above; keeled; 5 -veined. Lemma midvein ciliate; hairy below. Lemma lateral veins obscure; stopping well short of apex. Lemma surface pubescent; hairy on veins. Lemma margins ciliate; hairy below. Lemma apex acute. Palea 1 length of lemma. Palea keels scabrous; ciliolate; adorned in the middle. Apical sterile florets resembling fertile though underdeveloped.

FLOWER Lodicules 2; membranous. Anthers 3; 1.3–1.5 mm long.

FRUIT Caryopsis with adherent pericarp. Hilum punctiform.

DISTRIBUTION Europe: northern, central, southwestern, southeastern, and eastern. Africa: north and Macaronesia. Asia-temperate: Siberia, Soviet far east, Caucasus, western Asia, China, and eastern Asia. Asia-tropical: India. Australasia: Australia and New Zealand. Pacific: north-central. North America: Subarctic, western Canada, northwest USA, north-central USA, northeast USA, southwest USA, south-central USA, southeast USA, and Mexico. South America: Caribbean and southern South America.

NOTES Poeae. CEH.

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