Plants annual; not rhizomatous. Culms to 150 cm. Ligules 1.5-7 mm, truncate to broadly acute; blades 1.5-15 cm long, 2-11 mm wide, smooth, shiny green, apices acuminate. Panicles 0.5-8(8.5) cm long, 0.8-2 cm wide, ovoid to subcylindrical; branches not evident, the spikelets borne singly, not clustered. Spikelets homogamous, all spikelets with a bisexual floret; florets 3; disarticulation above the glumes, below the sterile florets. Glumes 3.8-6(8) mm long, 0.8-1.5 mm wide, keels smooth or scabridulous, narrowly to broadly winged distally, wings 0.1-0.5 mm wide, entire, smooth, lateral veins prominent, usually smooth, sometimes scabridulous, apices acute or acuminate; sterile florets 2, 1.5-2.5 mm, 1/2 or more the length of the bisexual florets, pubescent; bisexual florets 2.9-4.7 mm long, 0.9-1.8 mm wide, pubescent, shiny, stramineous when immature, brown when mature, apices acuminate to beaked; anthers 1.5-2 mm. 2n = 14.
Phalaris caroliniana grows in wet, marshy, and swampy ground. It is a common species in suitable habitats through much of the southern portion of the Flora region and in northern Mexico. It has also been found in Puerto Rico, where it may be an introduction, and in Europe and Australia, where it is undoubtedly an introduction.
Erect annual 3-9 dm; main cauline lvs mostly 5-12 cm נ4-8 mm; ligules 1-3 mm; infl 2-6 cm, cylindric to ellipsoid, spike-like and scarcely or not at all lobed; glumes 4.5-6 mm, glabrous on both sides, scabrous on the narrowly winged keel; sterile lemmas subulate, 1.5- 2.5 mm, pilose, fertile lemma 3-4.5 mm, appressed-pilose throughout; 2n=14. Waste places, roadsides, and wet fields; widespread in Mex. and s. U.S., n. in our range to Va., Md., Ky., and Mo.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.