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..
Panicum virgatum L. Sp. PI. 59. 1753.
P. virgatum var. cubense Griseb. Cat. PI. Cub. 233. 1866.
Panicum virgatum var. obtusion Wood, Am. Bot. & Fl.
Club 23: 150. 1896.
Culms erect from a creeping rootstock, 3°-6° tall, glabrous. Sheaths smooth and glabrous; blades elongated, 1° or more long, 3"-6" wide, flat, long-acuminate, narrowed toward the base, glabrous, rough on the margins; panicle 6'-2o' long, the lower branches 4'-10' long, rarely shorter, spreading or ascending; spikelets ovate, acute to acuminate, 1 1/2"-2 1/4" long; first scale acuminate, about one-half as long as the spikelet, 3-5-nerved; second scale generally longer than the others, 5-7-nerved, the third similar and usually subtending a palet and staminate flower; fourth scale shining, shorter than the others.
Culms erect from a creeping scaly branched root-stock, 1 1/2°-6° tall, much branched, compressed, stout, smooth. Sheaths compressed, glabrous, or the lower ones pubescent; blades 1° long or more, 2"-5" wide, acuminate; ligule very short; panicles pyramidal, 6'-16' long; axis and ascending branches scabrous; spikelets 1 1/2"-1 3/4" long, crowded, lanceolate, acuminate, curved, longer than the scabrous pedicels; first scale less than one-half as long as the spikelet; second and third scales curved at the apex, much exceeding the fourth scale which is minutely pubescent at the apex.
Moist soil, Rhode Island to Kansas, south to Florida and Texas. July-Sept.
Panicum rhizomatum Hitchc. & Chase, differing in smaller spikelets and narrower panicle, occurs from Virginia to Florida and Texas.
Panicum agrostoides Spreng. Pugill. 2: 4. 1815.
Culms erect,1 1/2º -3º tall, much branched, compressed, smooth. Sheaths compressed, glabrous, or sometimes hairy at the throat; ligule very short, naked; leaves 1° long or more, 2."-4" wide, acuminate; panicles pyramidal, 4'-12' long, terminating the culm and branches; primary branches of the panicle spreading, secondary appressed or divergent; spikelets 3/4"-1" long, acute, straight, on usually sparsely hairy pedicels; first scale 3-nerved, acute; second and third scales 5-nerved, about twice as long as the first and longer than the oval fourth scale, which is sessile.
Wet ground, Maine to Minnesota, south to Florida and Texas. July-Sept.