Poa autumnalis |
Poa chambersii |
|
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autumn bluegrass |
Chambers' bluegrass |
|
Habit | Plants perennial; not rhizomatous, not stoloniferous, loosely tufted. | Plants perennial; loosely tufted or with solitary shoots, short-rhizomatous. |
Culms | 23-86 cm tall, 0.8-1.8 mm thick, bases often decumbent. |
10-50 cm, erect or the bases decumbent, terete or weakly compressed; nodes terete, 0-1 exserted. |
Sheaths | closed for 1/3 – 1/2 their length; ligules 0.2-1.9(2.5) mm, smooth or obtuse; blades (0.5)1-4 mm wide, flat or folded, thin. |
closed for 1/3 – 7/8 their length, terete to slightly compressed, smooth, glabrous, bases of basal sheaths glabrous, distal sheath lengths (1.15)1.5-4.6(6.6) times blade lengths; collars smooth, glabrous; ligules 0.5-2(2.5) mm, smooth, truncate to obtuse; innovation blades similar to the cauline blades; cauline blades gradually reduced in length distally, 2-5 mm wide, flat or folded, smooth or the adaxial surfaces sparsely scabrous, primarily over the veins, apices broadly prow-shaped, flag leaf blades 0.7-6 cm. |
Basal branching | mainly pseudointravaginal. |
all or mainly extravaginal. |
Panicles | (5)8-20 cm, erect or lax, broadly pyramidal at maturity, open, sparse, lower axils sometimes sparsely pubescent; nodes with 1-2(4) branches; branches 5-12 cm, spreading to reflexed, straight, angled, angles scabrous, with 3-8 spikelets in the distal 1/4-1/3. |
2-9 cm, erect, lanceoloid to ovoid, tightly to loosely contracted, with 15-35 spikelets, proximal internodes shorter than 2 cm; nodes with 1-2 branches; branches 0.9-3.2 cm, erect to ascending or slightly spreading, terete, smooth or sparsely scabrous, with 1-4 spikelets. |
Spikelets | 3-8.2 mm, laterally compressed; florets 2-4(6); rachilla internodes smooth, sparsely softly puberulent. |
6-12 mm, lengths to 3 times widths, laterally compressed, not sexually dimorphic; florets 2-7; rachilla internodes 0.8-1.5 mm, smooth or sparsely scabrous, glabrous. |
Glumes | distinctly shorter than the adjacent lemmas, distinctly keeled, keels scabrous; lower glumes subulate to lanceolate, (1)3-veined; upper glumes lanceolate to broadly lanceolate; calluses usually glabrous, rarely sparsely and shortly webbed; lemmas (2.8)3-4.6 mm, lanceolate, distinctly keeled, keels and marginal veins short- to long-villous, hairs extending up 3/4 of the keel, lateral veins prominent, intercostal regions softly puberulent, smooth, apices obtuse, blunt; palea keels softly puberulent to short-villous for much of their length, apices scabrous; anthers 1-1.4(2.6) mm. |
3/5- 4/5 as long as the adjacent lemmas, distinctly keeled; lower glumes 3-veined; calluses of at least some proximal florets sparsely webbed, with 1-2 mm hairs, others glabrous, rarely all glabrous; lemmas 5-7 mm, lanceolate, 5-7-veined, distinctly keeled, smooth or sparsely finely scabrous, glabrous throughout or the keels and marginal veins sparsely softly puberulent over the proximal 1/4, lateral veins moderately prominent, intercostal regions glabrous, margins glabrous, apices acute; palea keels sparsely scabrous, intercostal regions glabrous; anthers vestigial (0.1-0.2 mm), aborted late in development, or 1.8-3.7 mm. |
2n | = 28. |
= unknown. |
Poa autumnalis |
Poa chambersii |
|
Distribution |
AL; AR; DC; DE; FL; GA; IL; IN; KY; LA; MD; MI; MS; NC; NJ; OK; PA; SC; TN; TX; VA; NU; QC; Greenland
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OR |
Discussion | Poa autumnalis grows primarily in the southeastern United States, being found in forests of the eastern and western Appalachian piedmont and coastal plain. It is readily distinguished from other perennial species of the eastern United States by its combination of glabrous calluses and pubescent palea keels. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Poa chambersii is known only from upland forest openings in the Cascades of western Oregon, where it is dioecious, and from high elevations on Steens Mountain in southeastern Oregon, where it is gynodioecious. It resembles P. rhizomata (see previous), but has more closed sheaths, shorter ligules, less pubescent or glabrous lemmas, and lacks a well-developed web. It approaches P. cusickii subsp. purpurascens (p. 562), but is rhizomatous and sexually reproducing. It differs from P. wheeleri (p. 546) in having glabrous sheaths and flat or folded, glabrous innovation blades. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 24, p. 514. | FNA vol. 24, p. 548. |
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Sylvestres | Poaceae > subfam. Pooideae > tribe Poeae > Poa > subg. Poa > sect. Madropoa > subsect. Poa |
Sibling taxa | ||
Name authority | Muhl. ex Elliott | Soreng |
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