27. Panicum verrucosum Muhl (warty panicum)

Map 687a

Plants annual. Flowering stems 20–120 cm long, 1–2 mm in diameter below the middle, relatively slender and wiry, circular in cross‑section or nearly so, erect to sprawling, glabrous. Leaves scattered along the stems. Leaf sheaths rounded or slightly keeled on the back, hairy only along the margins, the ligule 0.2–0.3 mm long, a short fringe of hairs, sometimes united at the very base. Leaf blades 3–20 cm long, 2.5–10.0 mm wide, firm, ascending to more commonly spreading, glabrous, light green, flat, the midvein prominent and raised on the undersurface. Inflorescences 4–20 cm long, with the primary branches slender and spreading, not spikelike, rebranched 1 or more times, the ultimate branches not appearing 1‑sided, the spikelets relatively few toward the branch tips, mostly very short‑stalked. Spikelets 1.7–2.2 mm long, narrowly obovate in outline, glabrous. Lower glume 0.5–0.8 mm long, 1/4–1/5 as long as the rest of the spikelet, triangular, bluntly pointed at the tip, faintly 1‑nerved or without apparent nerves, smooth or with a few small blisterlike warts or tubercles. Upper glume 1.7–2.1 mm long, elliptic‑obovate, sharply pointed at the tip, faintly 3‑ or 5‑nerved, the surface with abundant small blisterlike warts or tubercles. Lowermost floret sterile, without a palea, the lemma 1.7–2.1 mm long, elliptic‑obovate, faintly 3‑ or 5‑nerved, the surface with abundant small blisterlike warts or tubercles. Fertile floret 1.8–2.2 mm long, narrowly elliptic‑obovate, sharply pointed at the tip. Anthers 0.3–0.6 mm long. 2n=36. August–October.

Uncommon, known thus far from a single site in Scott County (eastern U.S. and adjacent Canada west to Michigan, Missouri, and Texas, mostly along the Atlantic and Gulf Coastal Plains). Moist depressions of sand prairies.

This unusual species was discovered by Paul McKenzie in 1998 after the present volume was already in production, and added at the last minute. In general appearance, it resembles P. hians, but it is easily distinguished by its light green foliage, annual habit, and warty spikelets.