19. Panicum obtusum Kunth (vine mesquite)

Pl. 171 e, f; Map 680

Plants perennial, producing long (to 3 m), vinelike stolons at the hardened, somewhat knotty, sometimes rhizomatous base in addition to the erect or ascending flowering stems. Flowering stems 25–80 cm long, round in cross‑section or somewhat flattened, glabrous, sometimes glaucous. Leaves scattered along the stems. Leaf sheaths glabrous or hairy, rounded or somewhat angled across the back, the ligule a membrane 1–2 mm long. Leaf blades 4–20 cm long, 3–7 mm wide, firm, ascending, glabrous or with a few hairs along the margins near the base, bluish green, sometimes glaucous. Inflorescences 5–15 cm long, with the primary branches erect or strongly ascending spikelike racemes, usually not rebranched, the spikelets in 2 uneven rows on 1 side of the axis of the raceme. Spikelets 2.5–4.0 mm long, elliptic to obovate in outline, rounded at the tip, glabrous. Lower glume 2.4–3.8 mm long, more than 3/4 to nearly as long as the rest of the spikelet, elliptic to obovate, rounded at the tip, strongly 5–9‑nerved. Upper glume 2.5–4.0 mm long, elliptic to obovate, rounded at the tip, strongly 5–9‑nerved. Lowermost floret usually staminate and with a well‑developed but not hardened palea, the lemma 2.5–4.0 mm long, elliptic, 5‑nerved. Fertile floret 2.6–3.6 mm long, elliptic, rounded at the tip. Anthers 1.5–2.5 mm long. 2n=20, 36, 40. June–October.

Introduced, known only from historical collections from Jackson County (southwestern U.S. west to Kansas, Arkansas, and Texas; Mexico). Moist, disturbed areas.