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 pratensis L. Sp. PI. 67. 1753.
P. pratensis var. angustifolia Kunth, Enum. 1: 353. 1833.
Glabrous, culms 1°-4° tall, from long running rootstocks, erect, simple, smooth. Sheaths often longer than the internodes; ligule 3/4" long or less, truncate; blades smooth or rough, £"-3" wide, those of the culm 2'-6' in length, the basal much longer; panicle 2 1/2'-8' in length, usually pyramidal, the branches spreading or ascending, sometimes flexuous, 1'-3' long, divided and spikelet-bearing above the middle; spikelets 3-5-flowered, 2"-2 1/2" long, exceeding their pedicels; scales acute, the lower unequal, glabrous, rough on the keel, the lower 1-nerved, the upper 3-nerved; flowering scales \\" long, webbed at the base, 5-nerved, the marginal nerves and midnerve silky-pubescent below, the intermediate ones naked.
In meadows, fields and woods, almost throughout North America. Widely cultivated for hay and pasture. Also in Europe and Asia. In North America probably indigenous only in the northern and mountainous regions. Variable. Natural or green-grass. Common meadow-grass. June-Aug.
Culms 1°-3° tall, erect, slender, simple, smooth and glabrous. Sheaths usually much shorter than the inter-nodes; ligule 1/2" long; blades 1" wide or less, smooth beneath, rough above, those of the culm 1 1/2'-6' long, the basal much longer; panicle 3'-9' in length, the branches long and slender, spikelet-bearing at the extremities, 2'-5' long; spikelets 3-5-flowered, 2 1/2-3" long; empty basal scales acute, the first 1-nerved, narrow, shorter than the broad 3-nerved second; flowering scales rounded or re-tuse at the apex, 1 1/2"-2" long, not webbed at the base, pubescent on the lower part, 5-nerved, the midnerve silky-pubescent for three-fourths its length.
In woods, New Jersey to Missouri, south to Florida and Texas. March-May.
Poa sylvestris A. Gray, Man. 596. 1848.
Culms 1°-3° tall, erect, slender, simple, slightly flattened, smooth, glabrous. Sheaths shorter than the in-ternodes; ligule 1/2" long or less; blades smooth beneath, rough above, 1"-3" wide, those of the culm 1 1/2'-6' in length, the basal much longer; panicle 3'-7' in length, the branches spreading or ascending, often reflexed in age, 1 1/2'-3' long, spikelet-bearing at the extremities; spikelets 2-4-flowered, 1"-2" long; empty basal scales acute, the lower 1-nerved, the upper longer and 3-nerved; flowering scales about 1 1/4" long, webbed at the base, obtuse, often pubescent below, 5-nerved, the midnerve pubescent nearly its entire length and the marginal nerves below the middle.
In thickets and meadows, New York to Wisconsin, Nebraska, south to Florida and Texas. Branches of the panicle sometimes reflexed when old. June-July.