6. Poa palustris L. (fowl bluegrass)

Pl. 180 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.

Steyermark (1963) noted that his earlier report of P. nemoralis L. from Jackson County (Palmer and Steyermark, 1935) was based upon misdetermined specimens of P. palustris. The specimens supporting the inclusion of this species in the state’s flora were all collected prior to 1920.