Poa cusickii |
Poa x limosa |
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Cusick's bluegrass |
hybrid bluegrass |
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Habit | Plants perennial, gynodioecious, or all pistillate, 10–60(70)cm long, usually densely cespitose with short rhizomes. | Plants perennial, sterile, pistillate, or bisexual, 20–80 cm tall; rhizomatous to loosely cespitose. |
Culms | 0.5–1.8 mm thick; nodes terete, 0–2 exserted. |
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Basal branching | intravaginal or intra- and extravaginal. |
intra- and extravaginal or partly extravaginal. |
Leaves | sheaths closed 25–75% of their length, bases of basal sheaths glabrous; collars smooth or scabrous, glabrous, ligules of cauline leaves 1–3(6)mm; tips truncate to acute, ligules of sterile shoots 0.2– 0.5(2.5)mm; tips usually truncate; blades involute to flat, 0.2– 3.5 mm wide; all about equal or the upper ones slightly reduced in length; upper surface usually densely scabrous or hispidulous to softly puberulent, infrequently nearly smooth and glabrous; lower surface smooth or scabrous; uppermost blade 0.5–5(6)cm. |
sheaths closed usually about 15% of their length; ligules 1–4 mm long, blades of tillers 0.5–2 mm wide; cauline blades flat, folded, 0.5–5 mm wide; smooth or scabrous. |
Inflorescences | usually erect, tightly or loosely contracted, narrowly lanceoloid to ovoid, 2–10(12) cm; spikelets 10–100; branches erect or steeply ascending, 0.5–4(5)cm long, 1–3(5) per node, with 1–15 spikelets. |
erect, usually contracted, sometimes interrupted, 5–15 cm; branches erect; less than 4 cm. |
Spikelets | broadly lanceolate to narrowly ovate; to 3 times as long as wide; (3)4–10 mm; florets 2–6; rachilla internodes 0.5–1.2 mm long. |
somewhat laterally compressed, 4–7 mm long; florets 2–5; rachilla internodes smooth. |
Glumes | lanceolate; lower glumes 3-veined, distinctly shorter than the lowest lemma. |
2.5–3.5 mm long; lower glumes 3-veined. |
Calluses | glabrous or with short; sparse, sometimes diffuse cobwebby hairs less than 25% of the lemma length. |
glabrous or with cobwebby hairs to 25% as long as the lemma. |
Lemmas | lanceolate to broadly lanceolate; (3)4–7 mm, distinctly keeled, membranous; smooth or sparsely to densely scabrous, glabrous throughout, or keels and/or marginal veins softly puberulent near the base; tips acute. |
narrowly lanceolate, 2.5–4.5 mm, distinctly to weakly keeled, glabrous throughout or keels and marginal veins sparsely long-villous; tips acute. |
Anthers | vestigial and 0.1–0.2 mm, aborted late in development, or well developed and 2–3.5 mm. |
aborted late in development or 1.3–2.2 mm. |
Poa cusickii |
Poa x limosa |
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Distribution | ||
Discussion | 4 subspecies. Poa cusickii is a common upland bluegrass with a dense inflorescence. It is usually densely cespitose, though some plants may have short rhizomes. Similar P. fendleriana has reduced uppermost flag blades, and lemmas with silky hairs on the keels and marginal veins. Poa leibergii has narrower leaves and usually longer ligules. Poa wheeleri can be misidentified as P. cusickii if the specimen is collected without its distinctive scabrous leaf sheaths. Poa pringlei, restricted to southwestern Oregon near the California border, has longer ligules, sheaths closed to about a third their length, and glabrous (to scabrous) lemmas. It is dioecious, whereas P. cusickii plants are bisexual or entirely pistillate. |
Wet alkaline meadows in sagebrush steppe. 1300–2200m. BR, BW. CA, NV; British Columbia, Alberta, Saskatchewan. Native and exotic. Poa × limosa is a hybrid of P. pratensis and P. secunda ssp. juncifolia. It is more or less rhizomatous like P. pratensis, but the spikelets are more nearly terete, and the lemma veins are glabrous or less hairy. |
Source | Flora of Oregon, volume 1, page 455 Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting |
Flora of Oregon, volume 1, page 460 Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting |
Sibling taxa | ||
Subordinate taxa | ||
Web links |
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