Poa sylvestris
Poa occidentalis
woodland bluegrass
New Mexican bluegrass, New Mexico bluegrass
30-120 cm, bases often decumbent.
20-110 cm.
closed for (1/20) 1/2-7/8 their length, terete, throats frequently ciliate near the point of fusion;
ligules 0.5-2.7 mm, smooth or sparsely scabrous, truncate to obtuse;
blades 0.7-5 mm wide, flat, thin, lax.
closed for (1/5)1/4 – 1/2(3/5) their length, distinctly compressed and keeled, usually densely retrorsely scabrous, rarely sparsely scabrous, margins not ciliate;
ligules 3-12 mm, densely scabrous, acute to acuminate;
blades (1.2)1.5-6(10) mm wide, flat, lax, apices broadly prow-shaped.
mainly pseudointravaginal.
mixed intra- and extra-vaginal.
(6.7)9-20 cm, open, narrowly conical at maturity;
nodes with (2)3-10 branches per node;
branches (2)3-7 cm, spreading to eventually reflexed, straight, angled, angles several, densely scabrous, with 1-11 spikelets.
(6)12-40 cm, lax, eventually open, spikelets numerous, with 2-7 branches per node;
branches (3)5-18(23) cm, eventually spreading or drooping, angled, angles densely scabrous, with (5)8-40(120) spikelets.
2.5-4.4 mm, laterally compressed;
florets 2-3(4);
rachilla internodes longer than (1)1.2 mm, smooth, glabrous.
(3)4-7(8) mm, laterally compressed, with 3-7 florets;
rachilla internodes shorter than 1 mm, smooth.
distinctly keeled, keels scabrous;
lower glumes 1(3)-veined;
upper glumes shorter than or subequal to the lowest lemmas;
calluses webbed;
lemmas 2.1-3.1 mm, broadly lanceolate, distinctly keeled, keels and marginal veins short-villous, extending to near the apices on the keels, lateral veins prominent, softly puberulent to short-villous, intercostal regions usually sparsely softly puberulent, smooth, apices obtuse to acute;
palea keels softly puberulent at midlength, apices finely scabrous;
anthers 1-1.8 mm.
distinctly keeled, keels scabrous;
lower glumes 2-3.5 mm, 1-veined;
upper glumes 2.5-4.2 mm, shorter than or subequal to the lowest lemmas;
calluses webbed;
lemmas 2.6-4.2 mm, narrowly lanceolate, distinctly keeled, scabrous distally, keels and marginal veins short- to long-villous, keel hairs extending to midlength, marginal vein hairs to 1/3 the lemma length, lateral veins and intercostal regions usually sparsely softly puberulent, lateral veins prominent, apices narrowly acute;
palea keels scabrous, glabrous;
anthers 0.3-1 mm.
= 28.
= 14, 28.
Poa sylvestris
Poa occidentalis
Poa sylvestris grows in southeastern Canada and throughout much of the eastern United States, mainly at low elevations in woodlands, especially in riparian zones. It is easily distinguished from P. wolfii (p. 514) by its smaller, more numerous spikelets and lemmas that are usually sparsely hairy between the veins. Plants from the middle Appalachian Mountains have been confused with P. paludigena (p. 572); P. sylvestris is usually larger, has more than 2 branches per panicle node, is pubescent between the lemma veins and palea keels, and has larger anthers.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Poa occidentalis grows in natural openings and disturbed sites in mixed coniferous forests of the southwestern United States. It is one of the three diploid species of Poa known to be native to North America. The tetraploid count was obtained from a single giant individual. Poa occidentalis has been confused with P. tracyi (p. 543), but P. occidentalis consistently has shorter, well-developed anthers and lacks rhizomes. It also usually has longer ligules relative to the blade width, and is shorter-lived. A few plants are intermediate in some characteristics. Small plants of P. occidentalis sometimes resemble P. reflexa (see next).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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