Plants perennial; cespitose or loosely colonial, rhizomatous. Culms 35-150 cm, simple or branched. Leaves cauline; ligules membranous, ciliate; blades not pseudopetiolate, flat. Panicles open or contracted, sometimes becoming racemose distally; disarticulation above the glumes and between the florets. Spikelets 4-50 mm, laterally compressed, with 2-many florets, lower 1-4 florets sterile. Glumes 2, subequal, shorter than the spikelets, glabrous, (2)3-9-veined, acute to acuminate; lemmas glabrous, 3-15-veined, compressed-keeled, keels serrate or ciliate, apices acuminate to acute, entire (rarely bifid); paleas glabrous, gibbous basally, 2-keeled, keels winged, wings glabrous, scabrous, or pilose; lodicules 2, fleshy, cuneate, 2-4-veined, lobed-truncate; anthers 1; ovaries glabrous; styles 2; style branches 2, plumose, reddish-purple at anthesis. Caryopses 1.9-5 mm, laterally compressed, brown to reddish-black or black, x = 12.
Del., Wis., W.Va., Fla., N.J., Tex., La., N.C., Tenn., S.C., Pa., N.Y., D.C, N.Mex., Va., Ala., Ark., Ill., Ga., Ind., Iowa, Ariz., Md., Kans., Okla., Ohio, Mo., Mich., Miss., Ky.
Chasmanthium, a genus of five species endemic to North America, grows primarily in the southeastern and south-central parts of the United States. It was formerly included in Uniola, but it is now recognized as a distinct genus.
|1||Panicle branches nodding or drooping; pedicels 10-30 mm long; calluses pilose; lower glumes 4.2-9.1 mm long; keels of fertile lemmas winged, the wings scabrous to pilose their full length; caryopses 2.9-5 mm long||Chasmanthium latifolium|
|1||Panicle branches erect or ascending; pedicels 0.5-2.5(5) mm long; calluses glabrous; lower glumes 1.2-5 mm long; keels of fertile lemmas not winged, scabridulous toward or at the apices; caryopses 1.9-3 mm long.||> 2|
|2||Spikelets 9.5-24 mm long; fertile lemmas 9-13-veined; caryopses enclosed at maturity; blades 7-16(33) cm long, lanceolate-fusiform; culms leafy for 80% of their height.||> 3|
|3||Axils of the panicle branches scabrous; fertile florets diverging to 45° from the rachilla; sterile florets (0)1(2); lower glumes 3.1-5 mm long, 7-9-veined; ligules entire||Chasmanthium nitidum|
|3||Axils of the panicle branches pilose; fertile florets diverging to 85° from the rachilla; sterile florets 2-4; lower glumes 2.5-2.9 mm long, 2-3-veined; ligules irregularly laciniate||Chasmanthium ornithorhynchum|
|2||Spikelets 4-10 mm long; fertile lemmas 3-9-veined; caryopses exposed at maturity; blades (8)20-50 cm long, linear-lanceolate; culms leafy for 40-50% of their height.||> 4|
|4||Collars and sheaths pilose; culms (1)2-3.5 mm thick at the nodes; fertile lemmas 7-9-veined, usually curved or irregularly contorted||Chasmanthium sessiliflorum|
|4||Collars and sheaths glabrous; culms to 1 mm thick at the nodes; fertile lemmas 3-7-veined, straight||Chasmanthium laxum|