6. Panicum clandestinum L.

Pl. 167 a, b; Map 667

Dichanthelium clandestinum (L.) Gould

Plants perennial, with rhizomes absent or more commonly short, forming clumps. Flowering stems 35–140 cm long, erect or ascending to arched, unbranched or the upper nodes becoming sparsely branched during the summer and autumn, the nodes glabrous or with short hairs (not bearded), the internodes glabrous or hairy. Foliage in a dense rosette of shorter, slightly broader leaves at the base and longer, somewhat narrower leaves well distributed along the main stems, those of the later branches usually somewhat shorter and narrower than those of the main stem leaves. Leaf sheaths hairy, sometimes only at the tip and along the margins, the hairs mostly with pustular bases, the ligule 0.3–1.0 mm long, a line or band of hairs, usually with a minute membrane at the base, rarely absent. Leaf blades of the main stems 10–28 cm long, 12–35 mm wide, ascending to spreading, heart‑shaped and somewhat clasping at the base, firm, hairy along the margins near the base, the hairs with pustular bases, glabrous on the surfaces, the midvein and larger lateral veins prominent and raised. Inflorescences 7–15 cm long, the earlier ones larger than the later ones, the branches loosely ascending to spreading, mostly rebranched 1 or more times, not spikelike or 1‑sided, the spikelets appearing mostly long‑stalked at the tips of the branches. Spikelets 2.5–3.5 mm long, elliptic‑obovate in outline. Lower glume 0.7–1.8 mm long, 1/3–1/2 as long as the spikelet, oblong‑ovate, bluntly to sharply pointed at the tip, glabrous or sparsely hairy, nerveless or faintly 1–5‑nerved. Upper glume 2.4–3.5 mm long, elliptic, rounded at the tip, 5–9‑nerved, hairy. Lowermost floret sterile and with a well‑developed, conspicuous palea, the lemma 2.4–3.5 mm long, elliptic, rounded or bluntly pointed at the tip, 5–9‑nerved, hairy. Fertile floret 2.2–3.0 mm long, elliptic, rounded to bluntly pointed at the tip. Anthers 0.3–1.4 mm long. 2n=18. May–September (vernal), July–November (autumnal).

Scattered to common throughout the state (eastern U.S. and adjacent Canada west to Iowa and Texas). Bottomland forests, mesic upland forests, moist depressions of prairies, and banks of streams; also roadsides, railroads, and moist, disturbed areas.

Panicum clandestinum is the most common and widespread of the Missouri species of subgenus Dichanthelium with relatively large, broad leaves with clasping bases. It differs from the other two, P. boscii and P. latifolium, in its leaf sheaths with pustular‑based hairs.