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..
Culms slender, smooth and glabrous, 1 1/2°-3° longr at length much elongated, dichotomously much branched and declining. Sheaths smooth and glabrous, or the lower ones pubescent, one-half the length of the internodes or less; ligule a short ring; blades erect, smooth and glabrous on both surfaces, lanceolate, principal nerves 5-7, the primary leaves l'-2 1/2' long, 1"-5" wide, those on the branches 1 1/2' or less long, concealing the small contracted panicles; primary panicle loose and open, 1 1/2'-3' long, its branches spreading or ascending, the lower 3/4'-1 1/2' long; spikelets on elongated pedicels, scattered, 1" long, oval to obovate, the scales glabrous, the first less than one-half as long as the spikelets.
P. yadkinense Ashe, Journ. E. Mitch. Sci. Soc. 16: 85. 1900.
A glabrous perennial. Culms up to 3º tall, finally somewhat branched; sheaths much shorter than the internodes, usually white-spotted; ligule less than \" long; blades 3'-5' long, 2"-6" wide, glabrous; panicle 3'-5' long, broadly ovate or oval, its branches long, ascending; spikelets about 1 1/4" long and 1/2 as wide, acute, elliptic, glabrous, the second and third scales longer than the fruiting scale.
Moist woods and thickets, Pennsylvania to Georgia, Illinois and Louisiana. June-Aug.
Panicum roanokense Ashe, of the southern states, differing by erect leaf-blades, and smaller turgid, strongly nerved spikelets, ranges north to Virginia.
P. barbulatum Nash, in Britt. & Br. 111. Fl. 1: 120.
Culms at first simple, erect, 2°-3° tall, later, profusely branched for their whole length, 3°-4° long, prostrate or leaning, the nodes strongly barbed; blades smooth and glabrous, generally truncate or rounded at the base, the primary ones 3'-5' long, about i' wide, widely spreading, the lower ones usually reflexed, those of the branches ¥-2' long, 1"-2" wide; primary panicle 3' - 5' long, exserted, ovoid, its branches ascending, rigid; secondary panicles smaller, lax, not exceeding the leaves, the branches bearing few spikelets; spikelets about 3/4" long, ellipsoid, purple, glabrous; first scale about one-third as long as the spikelet, acute.
Panicum nitidum Lam., differing by its larger pubescent spikelets, ranges from Virginia to Florida, the Bahamas and Texas.