Poa cusickii |
Poa bulbosa |
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Cusick's bluegrass |
bulbous 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 but often appearing annual, producing bulblets, 15–60 cm tall, green; cespitose. |
Culms | 0.5–1.8 mm thick; nodes terete, 0–2 exserted. |
bulbous at the base; nodes terete. |
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 about 25% of their length; basal sheaths swollen at the base; ligules 1–3 mm; blades flat, 1–2.5 mm wide; soon withering. |
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. |
ovoid, 3–12 cm; branches 2–5 per node, ascending to spreading. |
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. |
3–5 mm; florets 3–7, commonly all or all but the lowest producing bulblets, occasionally all producing seeds. |
Glumes | lanceolate; lower glumes 3-veined, distinctly shorter than the lowest lemma. |
keels scabrous; lower glumes 3-veined; upper glumes shorter than or subequal to lowest lemma. |
Calluses | glabrous or with short; sparse, sometimes diffuse cobwebby hairs less than 25% of the lemma length. |
with cobwebby hairs or 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. |
lanceolate, 3–4 mm, distinctly keeled, glabrous throughout, or keels and marginal veins shortto long-villous; area between veins glabrous or softly puberulent; tips acute. |
Anthers | vestigial and 0.1–0.2 mm, aborted late in development, or well developed and 2–3.5 mm. |
developed and 1.4–2 mm, or aborted late in development, or not developed. |
2n | =21–42. |
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Poa cusickii |
Poa bulbosa |
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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. |
Sunny to partly shady disturbed grasslands, shrub steppe, roadsides. 0–2300 m. All ecoregions except Est. CA, ID, NV, WA; throughout US; Mexico; temperate regions worldwide. Exotic. Poa bulbosa is usually recognized by the bulblets produced in the inflorescence. Occasional non-bulblet-producing plants can be recognized by their bulb-like shoot bases and the presence of bulb-bearing individuals nearby. Some botanists recognize two subspecies, P. b. ssp. bulbosa producing only normal caryopses and P. b. ssp. vivipara, producing bulblets. In Oregon, populations either are entirely viviparous or include both viviparous and seed-producing plants. |
Source | Flora of Oregon, volume 1, page 455 Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting |
Flora of Oregon, volume 1, page 454 Rob Soreng, Barbara Wilson, Richard Brainerd, Nick Otting |
Sibling taxa | ||
Subordinate taxa | ||
Synonyms | Poa bulbosa ssp. bulbosa, Poa bulbosa ssp. vivipara | |
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