15. Panicum leibergii (Vasey) Scribner

Pl. 166 a, b; Map 676

Dichanthelium leibergii (Vasey) Freckmann

Plants perennial, without rhizomes, forming tufts. Flowering stems 20–80 cm long, erect or somewhat arched, initially unbranched, becoming sparsely branched during the summer and autumn, the nodes and internodes glabrous or more commonly short‑hairy. 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 slightly shorter and narrower than those of the main stems. Leaf sheaths pubescent with spreading, pustular‑based hairs, the ligule 0.2–0.4 mm long, an inconspicuous line or band of hairs. Leaf blades of the main stems 3–12 cm long, 7–12(–18) mm wide, broadly rounded at the base, pubescent on both surfaces with at least some of the hairs pustular‑based, those of the upper surface sometimes sparse. Inflorescences 4–12 cm long, the earlier ones larger and more open with mostly spreading to loosely ascending branches, 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 3.0–4.1 mm long, elliptic to obovate in outline. Lower glume 1.5–2.5 mm long, 1/2–5/8 as long as the spikelet, broadly ovate, sharply pointed at the tip, glabrous or sparsely hairy, nerveless or faintly 1–5‑nerved. Upper glume 2.8–3.8 mm long, elliptic‑obovate, rounded at the tip, 5–9‑nerved, hairy, the hairs with pustular bases. Lowermost floret staminate and with a well‑developed, conspicuous palea, the lemma 2.8–3.8 mm long, elliptic‑obovate, rounded at the tip, 5–9‑nerved, hairy, the hairs with pustular bases. Fertile floret 2.4–3.4 mm long, elliptic, rounded to bluntly pointed at the tip. Anthers 0.6–1.8 mm long. 2n=18. May–August (vernal), June–September (autumnal).

Uncommon and widely scattered in Missouri (northeastern U.S. and adjacent Canada west to South Dakota and Missouri). Bottomland and upland prairies, bottomland forests, and mesic upland forests.