Achnatherum occidentale |
Achnatherum eminens |
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common western needlegrass, stiff needlegrass, velvet-leaf, western needle grass |
Southwestern needlegrass |
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Habit | Plants tightly cespitose, not rhizomatous. | Plants cespitose, shortly rhizomatous, bases knotty. | ||||||||
Culms | 14-120(180) cm tall, 0.3-2 mm thick, internodes glabrous or puberulent to densely pubescent; nodes 2-4, glabrous or pubescent. |
50-100 cm tall, 0.8-1.5 mm thick, glabrous; nodes 2-3. |
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Panicles | 5-30 cm long, 0.5-1.5 cm wide; branches appressed, straight, longest branches 1-7 cm. |
20-55 cm long, 3-8 cm wide, open, often enclosed to midlength at anthesis; lower branches 5-8 cm, ascending to divergent, flexuous. |
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Spikelets | appressed to the branches. |
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Glumes | subequal, 9-15 mm long, 0.6-0.9 mm wide; florets 5.5-7.5 mm long, 0.5-0.9 mm thick, fusiform, terete; calluses 0.8-1.2 mm, sharp, dorsal boundary of the glabrous tip with the callus hairs narrowly acute; lemmas evenly hair, hairs 0.5-1.5 mm at midlength, apical hairs somewhat longer than those below, sometimes similar in length to those at the base of the awns, sometimes longer, apical lobes 0.3-0.5 mm, membranous; awns 15-55 mm, twice-geniculate, first 2 segments evidently hairy, terminal segment glabrous or partly to wholly pilose, sometimes scabrous; paleas 2.2-3.5 mm, 2/5 – 3/5 as long as the lemmas, hairs at the tip usually shorter than 1 mm, frequently extending beyond the apices, apices rounded; anthers 2.5-3.5 mm, dehiscent, not penicillate. |
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Lower glumes | 5-12 mm long, 0.5-0.7 mm wide, 3-5-veined; upper glumes 1-4 mm shorter, 3-veined; florets 4-7.5 mm long, 0.5-0.9 mm thick, fusiform, terete; calluses 1-2 mm, sharp; lemmas evenly hairy, hairs 0.4-0.8 mm throughout, apical lobes not present; awns 35-70 mm, persistent, twice-geniculate, first 2 segments scabrous, terminal segment flexuous; paleas 1-2 mm, 1/3 – 1/2 as long as the lemmas, sparsely to moderately pubescent, apices rounded, flat; anthers 3-3.5 mm, dehiscent, a few penicillate, hairs about 0.3 mm. |
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Caryopses | 4-6 mm, fusiform. |
about 4 mm, fusiform. |
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Basal | sheaths glabrous or puberulent to densely pubescent, often ciliate at the throat; collars often with tufts of hair at the sides; ligules 0.2-1.5 mm, often ciliate; blades 0.5-3 mm wide and flat, or convolute and 0.1-0.8 mm in diameter, lax to straight. |
sheaths mostly glabrous, ciliate on the margins; collars glabrous on the back, usually with tufts of hair on the sides, hairs about 0.8 mm; basal ligules 0.8-1.6 mm, membranous, glabrous, rounded to acute; upper ligules to 4.5 mm, acute; blades 0.7-3.5 mm wide, abaxial surfaces smooth to scabridulous, adaxial surfaces prominently ribbed, scabridulous or sparsely to densely pubescent, hairs about 0.1 mm. |
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2n | =36. |
= 44, 46. |
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Achnatherum occidentale |
Achnatherum eminens |
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Distribution |
AZ; CA; CO; ID; MT; NV; OR; UT; WA; WY; AB; BC
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AZ; NM; TX
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Discussion | Achnatherum occidentale, which extends from British Columbia to California, Utah, and Colorado, varies considerably in pubescence and size. The three subspecies recognized here occasionally occur together. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Achnatherum eminens grows on dry, rocky slopes and valleys in the mountains of the southwestern United States, primarily in desert scrub, at 600-2600 m. Its range extends into Mexico. It is easy to recognize because of its open panicle, flexuous branches, and flexuous awns. It is superficially similar to Nassella cernua, but differs in its longer, glabrous ligules, not or weakly overlapping lemma margins, pubescent paleas, and geographic distribution. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 24, p. 121. | FNA vol. 24, p. 133. | ||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Stipeae > Achnatherum | Poaceae > subfam. Pooideae > tribe Stipeae > Achnatherum | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | Stipa occidentalis, Stipa occidentalis var. montana | Stipa eminens | ||||||||
Name authority | (Thurb.) Barkworth | (Cav.) Barkworth | ||||||||
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