Achnatherum occidentale |
Achnatherum scribneri |
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common western needlegrass, stiff needlegrass, velvet-leaf, western needle grass |
Scribner needlegrass, Scribner's needlegrass |
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Habit | Plants tightly cespitose, not rhizomatous. | Plants cespitose, not rhizomatous. | ||||||||
Culms | 14-120(180) cm tall, 0.3-2 mm thick, internodes glabrous or puberulent to densely pubescent; nodes 2-4, glabrous or pubescent. |
25-90 cm tall, 0.5-1.6 mm thick, glabrous; nodes 3. |
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Panicles | 5-30 cm long, 0.5-1.5 cm wide; branches appressed, straight, longest branches 1-7 cm. |
7-21 cm long, 0.5-1 cm wide; branches appressed to ascending, straight. |
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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 | 10-17 mm long, 0.7-1.2 mm wide, exceeding the upper glumes by 2.5-4.5 mm, apices tapering, often slightly recurved; florets 6-9.5 mm long, 0.6-1.1 mm thick, fusiform, terete, widest at or below midlength; calluses 0.5-1.5 mm, sharp; lemmas evenly hairy, hairs at midlength to 1 mm, apical hairs 2-3 mm, ascending, apical lobes 0.3-0.5 mm; awns 13-25 mm, persistent, usually once-geniculate, first segment scabrous, terminal segment straight; paleas 2.5-3.5 mm, 1/3 – 1/2 as long as the lemmas, pubescent, hairs not exceeding the apices, apices rounded; anthers 3-5 mm, dehiscent, not penicillate. |
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Caryopses | 4-6 mm, fusiform. |
5-6 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 becoming flat and papery, margins ciliate distally; collars glabrous, with tufts of hair on the sides, hairs on the basal leaves to 1.5 mm, hairs on the flag leaves 1-2.5 mm; basal ligules 0.3-0.8 mm, truncate, erose, ciliate, cilia 0.2-0.4 mm; upper ligules to 1.5 mm, asymmetric, obliquely truncate for most of their width, abruptly longer on 1 side; blades to 30 cm long, 2-5 mm wide, flat or involute, long-tapering. |
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2n | =36. |
= 40. |
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Achnatherum occidentale |
Achnatherum scribneri |
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Distribution |
AZ; CA; CO; ID; MT; NV; OR; UT; WA; WY; AB; BC
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CO; NM; OK; TX; WY |
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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 scribneri grows on rocky slopes, in pinyon-juniper and ponderosa pine associations at 1500-2700 m, from southeastern Wyoming through Colorado to Arizona, New Mexico, western Oklahoma, and Texas, and in Capital Reef National Park, Utah. At present, the Utah population appears to be disjunct from the species' primary range; this may reflect a lack of collecting. Achnatherum scribneri is similar to A. parishii, A. robustum, A. perplexum, and A. lobatum, differing from all of them in its sharp calluses. (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. 135. | ||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Stipeae > Achnatherum | Poaceae > subfam. Pooideae > tribe Stipeae > Achnatherum | ||||||||
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Subordinate taxa | ||||||||||
Synonyms | Stipa occidentalis, Stipa occidentalis var. montana | Stipa scribneri | ||||||||
Name authority | (Thurb.) Barkworth | (Vasey) Barkworth | ||||||||
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