Plants perennial; rhizomatous. Culms 60-120 cm, erect; nodes
glabrous. Sheaths glabrous; ligules 0.5-3 mm; blades
to 50 cm long, 0.2-2(8) mm wide, involute (rarely flat), glabrous, pubescent behind
the ligules. Panicles terminal, with 1-3 racemosely arranged branches;
branches 5.6-23.3 cm, erect (rarely divergent), terminating in a spikelet;
branch axes 0.5-1.2 mm wide, glabrous, margins scabrous to pubescent. Spikelets
2.3-3.7 mm long, 1.3-1.9 mm wide, paired, imbricate, appressed to the branch axes,
elliptic to narrowly ovate, glabrous, stramineous (rarely partially purple). Lower
glumes usually absent; upper glumes glabrous, 1-veined, margins entire;
lower lemmas glabrous, lacking ribs over the veins, 3-veined, margins entire;
upper florets stramineous. Caryopses 2-2.4 mm, yellow to golden
brown. 2n = unknown.
Paspalum monostachyum grows in sand and muck soils on coastal sand dunes,
wet prairie, marshes, and disturbed habitats of the southern coastal plain from
Florida to eastern Mexico.