Poa cusickii |
Poa cusickii ssp. cusickii |
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Cusick's bluegrass |
Cusick's bluegrass |
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Habit | Plants perennial, gynodioecious, or all pistillate, 10–60(70)cm long, usually densely cespitose with short rhizomes. | Plants gynodioecious and dioecious, 10– 60(70)cm; densely cespitose. |
Culms | 0.5–1.8 mm thick; nodes terete, 0–2 exserted. |
mostly erect; nodes 0–1; well exserted. |
Basal branching | intravaginal or intra- and extravaginal. |
intravaginal. |
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 25–67% of their length, blades of sterile shoots flat, folded, or involute, 0.5–1 mm wide; cauline blades less than 1.5 mm wide; uppermost blades (0.5)1.5–5 cm long; to 33% as long as their sheaths. |
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. |
contracted, usually 5–10(12)cm; spikelets 20–100; branches 1.7–4(5)cm, moderately to densely scabrous, with 2–15 spikelets. |
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. |
4–10 mm. |
Glumes | lanceolate; lower glumes 3-veined, distinctly shorter than the lowest lemma. |
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Calluses | glabrous or with short; sparse, sometimes diffuse cobwebby hairs less than 25% of the lemma length. |
glabrous. |
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. |
4–7 mm, glabrous. |
Anthers | vestigial and 0.1–0.2 mm, aborted late in development, or well developed and 2–3.5 mm. |
vestigial and 0.1–0.2 mm, or functional and 2–3.5 mm. |
2n | =28. |
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Poa cusickii |
Poa cusickii ssp. cusickii |
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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. |
Riparian meadows and swales in upper sagebrush zone to alpine slopes and ridges. 300–3000m. BR, BW, ECas, Lava, Owy. CA, ID, NV, WA. Native. This is the most widespread Poa cusickii subspecies, occurring from low elevations to the alpine zone. It is the only subspecies that sometimes produces functional anthers. It can be confused with Poa leibergii, which has longer ligules on the vegetative shoots and more spikelets in the inflorescence. |
Source | Flora of Oregon, volume 1, page 455 Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting |
Flora of Oregon, volume 1, page 456 Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting |
Sibling taxa | ||
Subordinate taxa | ||
Synonyms | Poa cusickii var. cusickii | |
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