4. Panicum boscii Poir.

Pl. 167 c, d; Map 665

P. boscii var. molle (Vasey) Hitchc. & Chase

Dichanthelium boscii (Poir.) Gould & C.A. Clark

D. boscii var. molle (Vasey) Mohlenbr.

Plants perennial, with rhizomes short or absent, forming tufts or more commonly clumps. Flowering stems 30–70 cm long, erect or ascending to arched, unbranched or the upper nodes becoming sparsely branched during the summer and autumn, the nodes with a conspicuous beard of downward‑pointing hairs, the internodes glabrous or minutely 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 somewhat shorter and narrower than those of the main stem leaves. Leaf sheaths usually hairy along the margins, glabrous or hairy on the surface, the ligule 0.5–1.0 mm long, a line or band of hairs. Leaf blades of the main stems 6–14 cm long, (9–)14–33 mm wide, ascending to spreading, heart‑shaped and somewhat clasping at the base, firm, hairy along the margins near the base, glabrous or hairy on the surfaces, the midvein and larger lateral veins prominent and raised. Inflorescences 4–25 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 3.7–5.2 mm long, elliptic‑obovate in outline. Lower glume 1.4–2.5 mm long, 1/3–1/2 as long as the spikelet, ovate, sharply pointed at the tip, glabrous or sparsely hairy, nerveless or faintly 1–5‑nerved. Upper glume 3.5–5.0 mm long, elliptic, rounded at the tip, 5–9‑nerved, hairy. Lowermost floret sterile or staminate and with a well‑developed, conspicuous palea, the lemma 3.5–5.2 mm long, elliptic, rounded at the tip, 5–9‑nerved, hairy. Fertile floret 3.2–4.0 mm long, elliptic, rounded to bluntly pointed at the tip. Anthers 0.3–1.4 mm long. 2n=18, 36. May–July (vernal), July–October (autumnal).

Scattered, mostly south of the Missouri River (eastern U.S. west to Illinois, Missouri, and Texas). Mesic to dry upland forests and less commonly ledges of shaded bluffs.

Panicum boscii is a characteristic species of ravines in the Ozarks. It is distinguished from P. clandestinum and P. latifolium, the two other Missouri species having relatively large, broad leaf blades with clasping bases, by its bearded stem nodes and longer spikelets. Some specimens of P. latifolium also have noticeably hairy nodes, but in these the hairs are not markedly differentiated from those of the internodes. Other species with clasping leaf bases, such as P. boreale and P. commutatum, have generally somewhat narrower leaf blades and shorter spikelets.