6. Poa palustris L. (fowl bluegrass)
g–i; Map 730
Plants perennial, without rhizomes but sometimes appearing
rhizomatous because of the prostrate stem bases that root at the lowermost
nodes, forming loose clumps. Flowering stems 30–90(–120) cm long, erect but
often prostrate at the base, circular in cross‑section or very slightly
flattened, glabrous. Leaf sheaths rounded, glabrous, the ligule (2.0)2.5–5.0 mm
long, bluntly pointed on the margin. Leaf blades 5–25 cm long, 1–2 mm wide,
flat or sometimes folded near the base, glabrous or sometimes roughened on the
upper surface. Inflorescences (8–)15–30 cm long, open, the lowermost nodes with
(2)3–5 branches, these spreading. Spikelets 2.5–4.5 mm long, with 2–4 fertile
florets. Lower glume 1.9–2.7 mm long, lanceolate to narrowly ovate, sharply
pointed at the tip, with broad, thin margins, 1‑nerved, roughened along
the midnerve. Upper glume 2.0–3.1 mm long, narrowly ovate, sharply pointed at
the tip, with broad, thin margins, 3‑nerved, roughened along the midnerve.
Lemmas 2–3 mm long, elliptic, sharply pointed at the tip, 3‑nerved, short‑hairy
along the nerves and with a tuft of long, cobwebby hairs at the base. Anthers
0.8–1.2 mm long. Fruits 1.3–1.8 mm long, reddish brown, shiny. 2n=21,
28, 29, 30, 32, 42. June–September.
Introduced, uncommon in Jackson County and eastern Missouri (native of Europe, Asia; naturalized widely from Alaska across Canada and south in the western U.S. to New Mexico and in the eastern U.S. to Missouri and
Virginia). Banks of rivers, railroads, and moist, disturbed areas.