25. Panicum scoparium Lam.

Pl. 168 a–d; Map 686

Dichanthelium scoparium (Lam.) Gould

Plants perennial, without rhizomes, forming tufts. Flowering stems 40–150 cm long, erect or spreading, initially unbranched, becoming much‑branched during the summer and autumn, the nodes densely bearded with relatively long, spreading to downwardly pointed hairs, the internodes with a well‑differentiated, broad, glabrous or glandular band below each node, otherwise pubescent with shorter, soft, gray, velvety hairs. Foliage in a dense rosette of shorter, somewhat broader leaves at the base and longer, narrower leaves well distributed along the main stems, those of the later branches even shorter and narrower. Leaf sheaths usually somewhat sticky‑glandular along the middle of the back, otherwise pubescent with soft, gray, velvety hairs, the ligule 0.6–1.8 mm long, an inconspicuous line or band of hairs. Leaf blades of the main stems 5–25 cm long, 6–20 mm wide, broadly rounded at the base, usually densely pubescent on both surfaces with soft, gray, velvety hairs. Inflorescences 6–15 cm long, the earlier ones larger and more open with mostly spreading to loosely ascending branches (later ones sometimes reduced to small clusters of long‑stalked spikelets), the branches mostly rebranched 1 or more times, not spikelike or 1‑sided, the spikelets appearing mostly long‑stalked at the tips of the branches. Spikelets 2.0–2.7 mm long, obovate in outline. Lower glume 0.4–1.5 mm long, 1/4–5/8 as long as the spikelet, broadly ovate, sharply pointed at the tip, glabrous or sparsely hairy, nerveless or faintly 1–5‑nerved. Upper glume 1.9–2.6 mm long, obovate, rounded at the tip or more commonly with an abrupt, short point, 5–9‑nerved, hairy. Lowermost floret sterile and with a reduced, inconspicuous palea, the lemma 1.9–2.6 mm long, obovate, rounded at the tip or more commonly with an abrupt, short point, 5–9‑nerved, hairy. Fertile floret 1.8–2.2 mm long, elliptic to slightly obovate, rounded or more commonly with an abrupt, short point at the tip. Anthers 0.2–0.9 mm long. 2n=18. June–August (vernal), July–November (autumnal).

Scattered in the Unglaciated Plains, Ozark, and Mississippi Lowlands Divisions (eastern U.S. west to Illinois, Kansas, and Texas; Mexico, Caribbean Islands). Bottomland and upland prairies, sand prairies, ledges of bluffs, glades, margins of sinkhole ponds, fens, and openings of mesic upland forests, usually on acidic and especially sandy substrates; also roadsides, railroads, and fallow fields.

Later in the growing season, stems of this species tend to take on a sprawling aspect and often grow over surrounding vegetation. The sticky bands below the nodes of the otherwise densely hairy stems are distinctive and make this species one of the easiest members of subgenus Dichanthelium to recognize.