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..
Poa alpina L. Sp. PI. 67. 1753.
Smooth and glabrous, culms 4'-18' tall, erect, simple. Sheaths shorter than the internodes; ligule 1" long, truncate; blades 1'-3' long, 1"-2" wide, abruptly acute; panicle 1'-3' in length, the branches generally widely spreading, 1' long or less; spikelets 3-5-flowered, 2 1/2"-3" long; lower scales broad, glabrous, rough on the keel, acute; flowering scales about 2" long, obtuse, pilose for half their length, pubescent between the nerves toward the base.
Newfoundland and Labrador to Alaska, south to Nova Scotia, Quebec, Lake Superior and Washington, and in the Rocky Mountains to Colorado. Also in Europe and Asia. Summer.
Poa glauca Vahl, Fl. Dan. pl. 964. 1790.
Poa caesia J. E. Smith, Eng. Bot. pl. 1719. 1807.
Culms 6'-2° tall, erect, rigid, glabrous, somewhat glaucous. Sheaths overlapping, confined to the lower half of the culm; ligule 1" long; blades l'-2' long, 1" wide or less, smooth beneath, scabrous above; panicle 1'-3' in length, open, the branches erect or ascending, 1/2'-l 1/2' long; spikelets 2-4-flowered, 2 1/2"-3" long; empty basal scales acute, 3-nerved, glabrous, rough on the upper part of the keel; flowering scales 1 1/2"-1 3/4" long, obtuse or acutish, rough, not webbed at the base, the lower half of the midnerve and marginal nerves silky-pubescent, the intermediate nerves obscure and occasionally sparingly pubescent at the base.
Greenland and Labrador to Maine and White Mountains of New Hampshire and Minnesota. Also in Europe. July and August.
Culms 1°-2 1/2° tall, erect, simple, smooth and glabrous. Sheaths shorter than the internodes, smooth or slightly rough; ligule 2" long, acute, decurrent; blades 1"-3" wide, smooth beneath, a little rough above and on the margins, those of the culm 1'-3 1/2' long, the basal 6'-10' in length; panicle 2'-5' long, open, the branches spreading or ascending, 1'-2' long; spikelets 3-5-flowered, 3"-4" long, exceeding their pedicels; lower scales nearly equal, acute, 3-nerved; flowering scales acutish, about 1 1/2" long, rough above, 5-nerved, pubescent between the nerves below, the marginal nerves and midnerve silky-pubescent about half their length.
Manitoba and Assiniboia to Nebraska and Colorado.
Poa trivialis L. Sp. PI. 67. 1753.
Culms 1°-3° tall, usually more or less decumbent at the base, simple, smooth or slightly scabrous. Sheaths usually shorter than the internodes, rough; ligule 2"-3" long, acutish; blades 2-7' in length, 1"-2" wide, generally very rough; panicle 4'-6' long, open, the branches usually spreading or ascending, 1'-2' long; spikelets 2-or sometimes 3-flowered, 1 1/2" long, exceeding their pedicels; scales acute, the empty basal ones rough on the keel, the lower 1-nerved, shorter than the 3-nerved upper; flowering scales 1"-1 1/2" long, webbed at the base, 5-nerved, the midnerve silky-pubescent below, the lateral nerves naked, the intermediate ones prominent.