13. Panicum latifolium L.

Pl. 166 c, d; Map 674

Dichanthelium latifolium (L.) Gould & C.A. Clark

Plants perennial, with rhizomes short or absent, forming clumps. Flowering stems 30–120 cm long, erect or ascending to arched, unbranched or the upper nodes becoming sparsely branched during the summer and autumn, the nodes and internodes glabrous or sparsely and inconspicuously 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 along the margins, glabrous on the surface or the lowermost sheaths sparsely and inconspicuously hairy, sometimes only at the tip, the hairs without 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 5–18 cm long, (9–)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 without pustular bases, glabrous on the surfaces, the midvein and larger lateral veins prominent and raised. Inflorescences 6–15 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 3.2–3.8 mm long, elliptic in outline. Lower glume 1.0–1.8 mm long, 1/3–1/2 as long as the spikelet, oblong‑ovate, sharply pointed at the tip, glabrous or sparsely hairy, nerveless or faintly 1–5‑nerved. Upper glume 3.0–3.8 mm long, elliptic, rounded or bluntly pointed at the tip, 5–9‑nerved, hairy. Lowermost floret sterile and with a well‑developed, conspicuous palea, the lemma 3.0–3.8 mm long, elliptic, rounded or bluntly pointed at the tip, 5–9‑nerved, hairy. Fertile floret 2.3–3.1 mm long, elliptic, bluntly pointed at the tip. Anthers 0.4–1.6 mm long. 2n=18. May–August (vernal), July–October (autumnal).

Scattered nearly throughout Missouri. (eastern U.S. and adjacent Canada west to Minnesota and Arkansas).

A few specimens from northern Missouri appear somewhat intermediate between this species and P. boscii. They have the stem nodes short‑hairy, but without a noticeable beard of longer hairs, the lower leaf sheaths with somewhat longer and denser hairs more typical of those found in P. boscii, and spikelets within the size range of P. latifolium. These specimens were referred to P. latifolium by Steyermark (1963). For clues on separating P. latifolium from two related Missouri species with broad leaves having heart‑shaped bases, see the treatments of P. boscii and P. clandestinum.