This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Generally tall perennial grasses, with long narrow flat leaves and terminal decompound panicles. Sessile spikelets consisting of 4 scales, the two outer indurated and shining, the inner hyaline, the fourth with a perfect, rarely imperfect, awn, and subtending a palet and perfect flower, or the palet sometimes wanting. Pedicellate spikelets wanting. Stamens 3. Styles distinct; stigmas plumose. Grain free. [Greek, resembling Sorghum.]
Awns 3 times as long as the spikelets or less; column straight, rarely geniculate.
Awns 4-5 times as long as the spikelets, the column geniculate.
Andropogon nutans L. Sp. PI. 1045. 1753.
Andropogon avenaceum Michx. Fl. Bor. Am. 1: 58. 1803.
Sorghum nutans A. Gray, Man. 617. 1848.
Chrysopogon avenaceus Benth; Vasey, Grasses U, S. 20. 1883.
Sorghastrum nutans Nash, in Small, Fl. SE. U. S, 66. 1903.
Culms erect, 3°-8° tall, smooth, the nodes pubescent; sheaths glabrous, or the lower pubescent; blades 2° or less in length, 2"-8" wide, long-acuminate, scabrous; panicle 4'-12' long; branches 2'-4' long, slender, erect-spreading; spikelets in pairs, or in 3's at the ends of the branches, erect or somewhat spreading; first scale of sessile spike-let 3"-4" long, acute, pubescent with long hairs; second scale glabrous; awn 5"-10" long, the column straight.
Sorghum nutans Linnaeanum Hack, in Mart. Fl. Bras. 23: 276. 1883.
Chrysopogon Elliottii C. Mohr, Bull. Torrey Club 24:
21. 1897. Sorghastrum Linnaeanum Nash, in Small, Fl. SE.
U. S. 66. 1903. Sorghastrum Elliottii Nash, N. Am. Fl. 17: 130. 1912.
Culms 3°-4 1/2° tall; sheaths smooth and glabrous; blades 1 1/2° long or less, up to 5" wide, very rough; panicle 6'-12' long, the apex usually nodding, its branches erect or nearly so, at least the lower ones much exceeding the internodes of the axis, 2 1/2-3' long, the ultimate divisions straight; spikelets 3"-4" long, lanceolate, deep chestnut brown at maturity, hirsute, the awn 1'-1 1/2' long, the column- geniculate.
In dry soil, Virginia and Tennessee to Florida and Texas.