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Aquatic and Wetland Vascular Plants of the Northern Great Plains

Poa L. -- Bluegrass


Tufted or rhizomatous perennials (those included here) of short to moderate stature, green or glaucous; culms erect to decumbent, hollow, sometimes compressed. Leaves mostly near the base, the blades flat to folded, the margins and midrib converging to a blunt, keeled leaf tip resembling the prow of a boat; sheaths partly closed, rounded or keeled; ligules membranous. Inflorescence an open to narrowly contracted panicle of small, mostly 2- to 8-flowered spikelets. Spikelets disarticulating above the glumes and between the florets; glumes subequal or the second a little longer than the first, acute; first glume 1- to 3-nerved; second glume 3-nerved; lemmas acute to blunt-tipped, reduced in size upward in the spikelet, faintly 5-nerved or appearing 3-nerved, with the intermediate nerves very obscure or obsolete, keeled or rounded on the back, often with a tuft of cobwebby hairs at the base, this sometimes scant, otherwise glabrous, scabrous or pubescent mainly on the nerves, sometimes pubescent or scabrous between the nerves as well; palea nearly as long as the lemma.

Lead Characteristic Go To
1 Culms strongly compressed, 2-edged; sheaths keeled. P. compressa
1 Culms round to slightly compressed, not 2-edged; sheaths rounded. Lead 2
2 Lemmas with a tuft of cobwebby hairs at the base, this sometimes scant; foliage green. Lead 3
2 Lemmas lacking a tuft of cobwebby hairs at the base, pubescent only on the keel and lateral nerves and sometimes between the nerves on the lower back; foliage glaucous. P. arida
3 Plants tufted, sometimes stoloniferous, lacking rhizomes; panicle diffuse and open (contracted when young), mostly 8-30 cm long. Lead 4
3 Plants extensively rhizomatous; panicle more compact, mostly 3-13 cm long. P. pratensis
4 Lemmas pubescent on the keel and on the marginal nerves toward the base, the intermediate nerves very fiant to obsolete. P. palustris
4 Lemmas pubescent on the keel only, not on the marginal nerves, the intermediate nerves prominent. P. trivialis

63. Poaceae, the Grass Family
23. Poa L. -- Bluegrass
1. Poa arida Vasey -- Plains bluegrass
2. Poa compressa L. -- Canada bluegrass
3. Poa palustris L. -- Fowl bluegrass
4. Poa pratensis L. -- Kentucky bluegrass
5. Poa trivialis L. -- Rough bluegrass


Return to Family -- Poaceae - The Grass Family
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