Poa pratensis, Kentucky bluegrass

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Intermountain Flora
Perennials with extensive creeping rhizomes, forming dense sods; culms (2) 3-6.5 (10) dm tall, slightly compressed, erect, with numerous innovations; sheaths smooth but occasionally somewhat scabrous, closed about half their length; lingules shorter than wide, 0.5-1.7 mm long, truncate, mostly entire, those on culm leaves may be as long as 3 mm; blades numerous, soft, usually green but occasionally glaucescent, flat or usually folded, about 1-3 (4.5) mm broad, usually with scabrous margins, sometimes slightly pubescent and purplish near the collar, the tips strongly boat-shaped; panicles open, often pyramidal, (2) 4-11 (16) cm long, with spreading or ascending braches usually in whorls of 4 or 5 (2-9); spikelets (3) 4-5 (6) mm long, ovate, crowded, 2- to 4-flowered, green or purplish, strongly compressed; glumes scabrous on the keel, the first glume 1.8-2.5 (3) mm long, 1-nerved, the second 2.2-3.3 mm long, 3-nerved; lemmas 2.5-4 mm long, 3- to 5-nerved, the lateral nerves weak, obtuse or acute, with copius cobwebby hairs at the base, the keel and marginal nerves with sericeous hairs, glabrous between the nerves; palea nearly equalling the lemma; anthers 0.8-1.9 mm long; lodicules about 0.7 mm long; 2n = 21-147 (it is not at all unusual to find several chromosome numbers represented in a single meadow).

Cronquist, A., Holmgren, A.H., Holmgren, N.H., Reveal, J.L., and Holmgren, P.K. (1977) "Intermountain Flora" pg. 232, vol. 6, The New York Botanical Garden New York.