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 scoparium Lam. Encycl. 4: 744. 1797.
P. pubcsccns Lam. Encycl. 4: 748. 1797.
P. viscidum Ell. Bot. S. C. & Ga. 1: 123. pl. 7. f. 3. 1817.
Culms erect, 2°-4° tall, simple or at length much branched above, villous. Sheaths shorter than the internodes, villous; blades generally narrowed, sometimes rounded or truncate at base, softly pubescent, those of the culm 4-7' long, 5"-8" wide, distant, those of the branches 1'-2 1/2' long, 2"-5" wide, crowded; primary panicle 3'-6' long, ovoid, branches ascending; secondary panicles much smaller, not exceeding the leaves; spikelets ovoid to oval, about 1 1/4" long, pubescent; first scale broadly ovate, about one-fourth as long as the spikelet; second and third scales nearly orbicular, 9-nerved, pubescent, the fourth oval, apicu-late, 1" long.
Moist soil, Massachusetts to New Jersey, Pennsylvania, Florida, Oklahoma and Texas. Cuba. June-Aug.
Culms 1°-2° tall, slender, finally somewhat branched above, papillose-hirsute with long spreading hairs, the nodes-densely barbed; sheaths papillose-hirsute with long spreading hairs; blades 2-4' long, 2V-6" wide, lanceolate, ascending, softly pubescent on both surfaces; panicle up to 2 1/2' long, its axis and spreading branches densely hirsute with spreading hairs; spikelets 1 1/4"-1 1/2" long, broadly oval or obo-void, densely hirsute with long spreading hairs.
P. scabriusculum Ell. Bot. S. C. & Ga. 1: 121. 1817.
Culms up to 6° tall, roughened, glabrous or minutely pubescent, finally branched; sheaths nearly glabrous or papillose-hispid; ligule very short; blades 4's' long, 4"-6" wide, ascending or spreading, sometimes reflexed, linear-lanceolate, glabrous; panicle 4'-8' long, its branches spreading or ascending; spikelets lanceolate, glabrous or minutely pubescent, strongly nerved, acute, about 1 1/4" long and i" wide, ovate to ovate-lanceolate.
In swampy places and ponds, Maryland to West Virginia, Florida and Texas. May-Aug.
Panicum cryptanthum Ashe, differs by its smaller size, glabrous sheaths, and unbranched culms, and occurs from New Jersey to Florida and Texas.
P. aculeatum Hitchc. & Chase, xlhodora, 8: 209. 1906.
Culms 3°-4° tall, tufted, rough, sometimes hispid below; sheaths papillose-hispid, or the upper ones glabrous; ligule a mere ring; blades 4's' long, 4"-7" wide, linear, elongated, stiff, ascending or erect, usually rough; panicle 3'-5' long, nearly as wide, its branches spreading or ascending; spikelets 1 1/2" long, elliptic, glabrous or nearly so, the first scale 1/2-1/3 as long as the spikelet, the second and third scales neither so prominently nor so sharply nerved as in the above species.
In swampy woods, New York to District of Columbia and North Carolina. July.