Poa palustris

HABIT Perennial; caespitose. Stolons absent, or present. Butt sheaths herbaceous. Culms erect, or geniculately ascending, or decumbent; 30–150 cm long; 3–4 -noded. Culm-internodes terete; smooth. Lateral branches lacking. Leaves mostly basal. Leaf-sheaths keeled; smooth. Ligule an eciliate membrane; 2–5 mm long; obtuse, or acute. Leaf-blades 5–20 cm long; 2–4 mm wide; flaccid. Leaf-blade surface scaberulous; glabrous. Leaf-blade margins scaberulous. Leaf-blade apex abruptly acute.

INFLORESCENCE Inflorescence a panicle.

Panicle open; oblong, or ovate; effuse; equilateral, or nodding; 10–30 cm long; 5–15 cm wide. Primary panicle branches spreading; 3–6 -nate. Panicle branches flexuous; scaberulous.

Spikelets solitary. Fertile spikelets pedicelled. Pedicels 1–5 mm long.

FERTILE SPIKELETS Spikelets comprising 2–5 fertile florets; with diminished florets at the apex. Spikelets oblong, or ovate; laterally compressed; 3–5 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes definite; obscured by lemmas; smooth. Floret callus woolly.

GLUMES Glumes persistent; similar; shorter than spikelet. Lower glume lanceolate; 2–3 mm long; 0.8–1 length of upper glume; membranous; 1-keeled; 1–3 -veined. Lower glume primary vein scabrous. Lower glume apex acuminate. Upper glume elliptic, or ovate; 2.5–3 mm long; 1 length of adjacent fertile lemma; membranous; 1-keeled; 3 -veined. Upper glume primary vein scabrous. Upper glume apex acuminate.

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

FLOWER Lodicules 2; membranous. Anthers 3; 1.3–3.5 mm long.

FRUIT Caryopsis with adherent pericarp. Hilum punctiform.

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

NOTES Poeae. CEH.

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