9. Paspalum setaceum Michx.
Pl. 172
h–j; Map 698
Plants perennial, with hardened, knotty bases, sometimes
with very short rhizomes, forming tufts or clumps. Flowering stems 30–100 cm
long, erect or ascending. Leaf sheaths hairy, sometimes only along the margins,
the ligule 0.4–1.0 mm long. Leaf blades 2–25 cm long, 3–15 mm wide, glabrous or
nearly so to variously hairy. Inflorescences with the 1–4 spikelike branches
mostly more than 2 cm apart along the main axis. Spikelike branches 3–12 cm
long, erect to spreading, the axis persistent, with a spikelet at the tip,
narrow and unwinged, narrower than the spikelets, the spikelets dense and
mostly strongly overlapping along the axis, mostly paired (from a short, forked
stalk) and appearing in 4 rows. Spikelets 1.4–2.8 mm long, broadly elliptic‑obovate
to nearly circular in outline, rounded or bluntly pointed at the tip. Lower
glume absent. Upper glume 1.4–2.8 mm long, broadly elliptic‑obovate to
nearly circular, rounded to bluntly pointed at the tip, 3–5‑nerved,
glabrous or hairy. Sterile floret with the lemma 1.4–2.8 mm long, broadly
elliptic‑obovate to nearly circular, rounded to bluntly pointed at the
tip, 2‑ or 3‑nerved, glabrous or hairy. Fertile floret with the
lemma 1.2–2.7 mm long, broadly elliptic to nearly circular. Anthers 0.8–1.2 mm
long. 2n=20, 40, 50. May–October.
Scattered to common nearly throughout the state (eastern U.S. west to Minnesota and Arizona; Mexico, Central America, Caribbean Islands). Upland prairies,
sand prairies, sandstone glades, savannas, mesic to dry upland forests, margins
of ponds and sinkhole ponds, banks of streams and rivers, and marshes; also
pastures, old fields, fallow fields, roadsides, railroads, ditches, and open,
disturbed areas.
Banks (1966) treated P. setaceum as consisting of nine
overlapping varieties, some of which had been treated as separate species by
earlier authors (Steyermark, 1963; Crins, 1991). Four of these varieties have
been confirmed for Missouri. Some specimens can be quite difficult to assign to
variety.