Achnatherum occidentale |
Achnatherum stillmanii |
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common western needlegrass, stiff needlegrass, velvet-leaf, western needle grass |
Stillman's needlegrass, Stuxman's needlegrass |
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Habit | Plants tightly cespitose, not rhizomatous. | Plants shortly rhizomatous, forming open clumps. | ||||||||
Culms | 14-120(180) cm tall, 0.3-2 mm thick, internodes glabrous or puberulent to densely pubescent; nodes 2-4, glabrous or pubescent. |
60-150 cm tall, 2-5 mm thick, often geniculate at the lowest node, mostly glabrous; nodes 2-3, often puberulent. |
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Panicles | 5-30 cm long, 0.5-1.5 cm wide; branches appressed, straight, longest branches 1-7 cm. |
10-24 cm long, 1.5-3 cm wide, contracted; branches straight, appressed to strongly ascending, lower branches 2.5-3.5 cm. |
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Spikelets | appressed to the branches. |
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. |
subequal, 14-16 mm; lower glumes 1-3-veined; upper glumes 0.6-1.5 mm wide, 3-5-veined; florets 8-10 mm, fusiform; calluses 0.5-1.2 mm, rounded; lemmas evenly hairy, hairs about 0.5 mm, apical hairs similar in length, apices 2-lobed, lobes 1-3 mm, narrow; awns 18-25 mm, persistent, scabrous, once- or twice-geniculate, terminal segment straight; paleas as long as or slightly longer than the lemmas, hairy, hairs about 0.5 mm, veins prolonged, reaching almost to the tips of the lemma lobes; anthers 4-6 mm, penicillate, dehiscent. |
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Caryopses | 4-6 mm, fusiform. |
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, sometimes ciliate distally, intact at maturity; collars glabrous or pubescent, often with hairs at the sides, hairs shorter than 0.5 mm; basal ligules 0.2-0.5 mm, membranous, truncate, ciliate, cilia 0.2-0.3 mm; upper ligules shorter than the basal ligules; blades 3-7 mm wide, lax. |
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2n | =36. |
= unknown. |
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Achnatherum occidentale |
Achnatherum stillmanii |
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Distribution |
AZ; CA; CO; ID; MT; NV; OR; UT; WA; WY; AB; BC
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CA |
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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 stillmanii grows at scattered locations in coniferous forests in northern California, at 900-1500 m, possibly being edaphically restricted. Its combination of large size, long, narrow lemma lobes, and paleal morphology distinguish A. stillmanii from all other North American species of Achnatherum. (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. 118. | ||||||||
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 stillmanii | ||||||||
Name authority | (Thurb.) Barkworth | (Bol.) Barkworth | ||||||||
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