Achnatherum nelsonii |
Achnatherum wallowaense |
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Columbia needle grass, Nelson achnatherum, Nelson's needlegrass |
Wallowa needlegrass |
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Habit | Plants cespitose, not rhizomatous. | Plants tightly cespitose, not rhizomatous. | ||||
Culms | 40-175 cm tall, 0.7-2.4 mm thick, lower cauline internodes usually glabrous, sometimes slightly pubescent below the lower nodes; nodes 2-5. |
(10)15-40 (45) cm tall, 0.5-0.7 mm thick, glabrous; nodes 1-2. |
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Panicles | 9-36 cm long, 0.8-2 cm wide; branches ascending to appressed, straight. |
(4)5-13(15) cm long, to 10 cm wide, lax; branches divergent, flexuous, longest branches 2-10 cm, with spikelets confined to the distal portions, drooping. |
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Spikelets | appressed to the branches. |
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Glumes | 6-12.5 mm long, 0.7-1.1 mm wide; lower glumes exceeding the upper glumes by 0.2-0.8 mm; florets 4.5-7 mm long, 0.6-0.9 mm thick, fusiform; calluses 0.2-1 mm, blunt to sharp, dorsal boundary of the glabrous tip with the callus hairs almost straight to acute; lemmas evenly hairy, hairs at midlength 0.5-1 mm, hairs at the apices to 2 mm, erect to ascending, apical lobes 0.1-0.4 mm, membranous, flexible; awns 19-45 mm, persistent, twice-geniculate, first 2 segments scabrous or with hairs shorter than 0.5 mm, terminal segment straight; paleas 2-4 mm, 1/3 – 2/3 as long as the lemmas, pubescent, hairs usually not exceeding the apices, veins terminating before the apices, apices rounded; anthers 2-3.5 mm, dehiscent, not penicillate. |
obtuse to acute; lower glumes 3.5-7 mm long, 0.8-1.3 mm wide, 5(7)-veined; upper glumes 3-6.5 mm, 3-veined; florets 3-5.5 mm long, 1-1.5 mm thick, fusiform, terete; calluses 0.1-0.2 mm, blunt; lemmas coriaceous, shiny, glabrous, black to dark brown at maturity, margins overlapping at maturity, apices thickened dorsally; awns 5-11 mm, readily deciduous, not or weakly geniculate, scabrous; paleas 2.8-4.5 mm, similar to the lemmas in texture, glabrous; anthers 1.6-1.8 mm, dehiscent, not penicillate. |
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Caryopses | 3-4 mm, fusiform. |
2-4 mm, ovoid. |
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Basal | sheaths glabrous or sparsely to densely pubescent, margins sometimes ciliate; collars glabrous or somewhat pubescent, without tufts of hair on the sides, collars of the flag leaves glabrous or sparsely pubescent; basal ligules 0.2-0.7 mm, membranous, truncate to rounded, usually not ciliate; upper ligules 1-1.5 mm, acute; blades (0.5)1.2-5 mm wide. |
sheaths becoming flat with age, glabrous; collars glabrous, including the sides; basal ligules 0.8-1.3 mm, membranous, truncate to broadly acute, glabrous; upper ligules to 1.6 mm; blades tightly valvate to involute, 0.5-0.8 mm in diameter, abaxial surfaces scabridulous, adaxial surfaces hairy, sometimes densely hairy, hairs shorter than 0.05 mm. |
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2n | = 36, 44. |
= unknown. |
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Achnatherum nelsonii |
Achnatherum wallowaense |
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Distribution |
AZ; CA; CO; ID; MT; NM; NV; OR; SD; TX; UT; WA; WY; AB; BC; SK; YT
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OR |
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Discussion | Achnatherum nelsonii grows in meadows and openings, from sagebrush steppe and pinyon-juniper woodlands to subalpine forests, at 500-3500 m. It flowers in late spring to early summer, differing in this respect from A. perplexum. It is sometimes sympatric with A. lettermanii, from which it differs in its shorter paleas and wider leaves, and its tendency to grow in deeper or less disturbed soils. It differs from A. lemmonii in having wider leaf blades, shorter paleas, and membranous lemma lobes, and from A. nevadense and A. occidentale in its scabrous awns and the truncate to acute boundary of the glabrous tip of the callus with the callus hairs. The two subspecies intergrade to some extent. There is also intergradation with Achnatherum occidentale, possibly as a result of hybridization and introgression. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Achnatherum wallowaense grows in shallow, rocky soil at scattered localities, from 1000-1600 m, in the Wallowa and Ochoco mountains, Oregon. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 24, p. 123. | FNA vol. 24, p. 138. | ||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Stipeae > Achnatherum | Poaceae > subfam. Pooideae > tribe Stipeae > Achnatherum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Stipa williamsii, Stipa occidentalis var. nelsonii, Stipa nelsonii | |||||
Name authority | (Scribn.) Barkworth | J.R. Maze & K.A. Robson | ||||
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