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..
Avena sativa L. Sp. PI. 79. 1753.
A glabrous annual. Culms up to 30 tall; blades flat, up to 1° long and 1/2' wide, acuminate; panicle 4'-9' long, its branches ascending; spikelets, exclusive of the awns, 8"-12" long, the empty scales broad, acute, the flowering scales glabrous, awnless, or with an imperfect awn which is rarely a little spiral at the base.
Persisting in old fields and as a weed along roadsides and waste places. A native of Europe and Asia.
Not Avena purpurascens DC. 1813.
Culms 1°-2° tall, erect, simple, slender, smooth and glabrous. Sheaths shorter than the internodes, smooth or slightly scabrous; ligule 1/2" long or less; blades erect, 1'-6' long, l"-3" wide, smooth beneath, usually scabrous above; panicle 2 1/2'-5' in length, lax, the branches erect or ascending, naked below, the lower 1'-2 1/2' long; spikelets 3-6-flowered, the empty scales smooth, the second 3"-3 1/2" in length, 3-nerved, the first two-thirds to three-quarters as long, 1-nerved; flowering scales 3"-4" long, with a ring of short hairs at the base, strongly nerved, scabrous; awns as long as the scales or longer.
In woods, New Brunswick to British Columbia, Pennsylvania, Minnesota and Colorado. July-Aug.
Culms 2 1/2°-5° tall, erect, simple, scabrous. Sheaths shorter than the internodes, very rough; ligule 2" long; blades 4's' long, 3"-6" wide, scabrous; panicle 6'-12' in length, the branches finally spreading; spikelets 3-6-flow-ered; empty scales smooth, the second 3"-4" in length, 5-nerved, the first shorter, obscurely 3-nerved; flowering scales 5" long, naked at the base, strongly nerved, scabrous, bearing an awn one-fourth to one-half their length.
Northern Michigan and Isle Royale. Summer.
A. pratensis americana Scribn. in Macoun, Cat. Can. PI.
2: 243. 1888. A. Hookeri Scribn. True Grasses 123. 1890. A. americana Scribn. Bull. U. S. Dep. Agr. Agrost.
7: 183. 1897.
A glabrous perennial. Culms tufted, 6'-i8' tall, erect; sheaths keeled; blades erect, up to 4' long, fiat, thick, the midnerve thickened as are the rough margins, linear, acute, those on the culm up to 2" wide, those of the innovations much narrower; panicle contracted, 2'-4' long, its branches erect; spikelets, exclusive of the awns, 6"-7" long, the empty scales acute, scarious above, the second equalling the spikelet or nearly so, the flowering scale 4 1/2"-6" long, brown and firm at the base, scarious above the middle, acute, the awn inserted about the middle, about 1/2 long and bent near the middle, spiral at the base.
On ridges and hillsides, Saskatchewan to South Dakota, west to Alberta and Colorado. June-Aug.
Avena pubescens Huds., of Europe, reported as adventive in Vermont and New Jersey, can be distinguished by its pubescent foliage and the very long hairs on the rachilla.