Achnatherum nelsonii |
Achnatherum lettermanii |
|||||
---|---|---|---|---|---|---|
Columbia needle grass, Nelson achnatherum, Nelson's needlegrass |
Letterman needlegrass, Letterman's needlegrass |
|||||
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. |
15-90 cm tall, 0.5-0.8 mm thick, usually glabrous, sometimes puberulent to 5 mm below the lower nodes; nodes 2-3. |
||||
Panicles | 9-36 cm long, 0.8-2 cm wide; branches ascending to appressed, straight. |
7-19 cm long, 0.5-1 cm wide; branches straight, appressed to strongly ascending, longest branches 1.2-2.5 cm. |
||||
Spikelets | appressed to the branches. |
appressed to the branches. |
||||
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. |
6.5-9 mm, subequal; lower glumes 1(3)-veined; upper glumes to 0.5 mm shorter than the lower glumes, 0.6-1 mm wide, 1-veined; florets 4.5-6 mm long, 0.8-1 mm thick, fusiform, teret, widest below midlength; calluses 0.4-1 mm, blunt; lemmas evenly hairy, hairs at midlength about 0.5 mm, apical hairs 0.7-1.5(2) mm, apical lobes 0.3-0.8, membranous, flexible; awns 12-25 mm, persistent, twice-geniculate, scabrous, terminal segment straight; paleas 3-4 mm, 3/4 - 4/5(9/10) as long as the lemmas, veins terminating at or before the apices, apices round, flat, apical hairs 0.5-1 mm, extending beyond the palea body; anthers 1.5-2 mm, dehiscent, not penicillate. |
||||
Caryopses | 3-4 mm, fusiform. |
about 4 mm, fusiform. |
||||
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 smooth, glabrous, margins not ciliate; collars, including the sides, glabrous or sparsely pubescent, collars of the flag leaves glabrous; ligules 0.2-1.5(2) mm, without tufts of hair on the sides, truncate to rounded; blades 0.5-2, wide, abaxial surfaces smooth to scabridulous, adaxial surfaces scabrous or puberulent. |
||||
2n | = 36, 44. |
= 32. |
||||
Achnatherum nelsonii |
Achnatherum lettermanii |
|||||
Distribution |
AZ; CA; CO; ID; MT; NM; NV; OR; SD; TX; UT; WA; WY; AB; BC; SK; YT
|
AZ; CA; CO; ID; MT; NM; NV; OR; UT; WY
|
||||
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 lettermanii grows in meadows and on dry slopes, from sagebrush to subalpine habitats, at 1700-3400 m. Its range extends from Oregon and Montana to southern California, Arizona, and New Mexico; it is not known from Mexico. When sympatric with A. nelsonii, A. lettermanii tends to grow in shallower or more disturbed soils. It can be distinguished from that species by its generally finer leaves and more tightly cespitose growth habit, as well as its blunter calluses and longer paleas. Its relatively long paleas also distinguish A. lettermanii from A. perplexum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
||||
Key |
|
|||||
Source | FNA vol. 24, p. 123. | 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 williamsii, Stipa occidentalis var. nelsonii, Stipa nelsonii | Stipa lettermanii | ||||
Name authority | (Scribn.) Barkworth | (Vasey) Barkworth | ||||
Web links |
|