Plants perennial; cespitose, rhizomatous, rhizomes short (less than 1 cm), forming a knotty base. Culms 50-175 cm, erect; nodes glabrous. Sheaths glabrous or pubescent, lower sheaths more frequently pubescent than the upper sheaths; ligules 1.5-3.8 mm; blades to 35 cm long, 2-16.5 mm wide, flat, mostly glabrous, adaxial surfaces with a few long hairs near the base. Panicles terminal, with 2-7 racemosely arranged branches; branches 1.5-12 cm, racemose, divergent; branch axes 0.7-1.4 mm wide, winged, glabrous, margins scabrous, terminating in a spikelet. Spikelets 2.3-4 mm long, 1.7-2.5 mm wide,paired, appressed to the branch axes, ovate, tapering to an acute apex, stramineous (rarely purple). Lower glumes absent; upper glumes and lower lemmas 5-7-veined, margins pilose; upper florets stramineous. Caryopses 2-2.3 mm, white to brown. 2n = 20, 40, 50-63.
Paspalum dilatatum is native to Brazil and Argentina. It is now well established in the Flora region, generally as a weed in waste places. It is also used as a turf grass.
Common Name: dallisgrass
Duration: Perennial
Nativity: Non-Native
Lifeform: Graminoid
General: Introduced perennial from hard, knotty base, stems 50-150 cm tall.
Vegetative: Basal sheaths often open soft-hairy below, above usually glabrous compressed; blades flat 3-12 mm wide, glabrous or pubescent, with few long hairs on axial surface above ligule; ligule membranous 1.5-3 mm long.
Inflorescence: Usually 3-5 spicate branches, mostly 5-8 cm long, single at the nodes, rachis broad and thin; spikelets 3-3.5 mm long about 2 mm broad, acute, abruptly pointed; first glume absent; second glume three-nerved, pubescent with long, soft hairs on margins and at base, glabrate on back; sterile lemma flat, glabrous or minutely puberulent, three-nerved; grain nearly orbicular.
Ecology: Found on open ground, mostly in moist or marshy soils, roadsides, and disturbed ground below 4,500 ft (1372 m).
Distribution: Throughout much of the world on every continent; most of the southern US, from OR south to CA and east to NJ; south through the Greater Antilles to S. Amer..
Notes: Found mostly in riparian areas distinguished by being an ascending to erect, rhizomotous perennial with knotty bases (P. distichum is spreading often decumbent with many stolons) and the singe-floret, hairy spikelets (P. distichum are glabrous) which are tightly appressed and ranked along the spike, often with purple stigmas sticking out.
Ethnobotany: Unknown
Etymology: Paspalum is from the Greek paspalos for millet, while dilatatum means spread out.
Synonyms: None
Editor: SBuckley 2010, FSCoburn 2015
Stout, erect, 8-15 dm; foliage glabrous, or the lowest sheaths sparsely villous; blades to 3 dm, 8-12 mm wide; racemes 3-6, spreading or ascending, 8-12 cm, the panicle much surpassing the reduced upper lf; spikelets ovate, acute, 2.9-3.8 mm; glume pubescent and near the margin long-villous; sterile lemma nearly glabrous; fertile lemma shorter and blunt; 2n=40, 50, 60+. Pastures, waste ground, and occasionally in moist fields or woods, native of S. Amer., cult. and widely escaped in s. U.S., extending n. to Ky. and in the coastal states to N.J.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
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