Achnatherum robustum
Achnatherum eminens
sleepy grass
Southwestern needlegrass
100-230 cm tall, 2-4.5 mm thick, mostly glabrous, often pubescent below the nodes, the pubescence antrorse or retrorse;
nodes 4-5.
50-100 cm tall, 0.8-1.5 mm thick, glabrous;
nodes 2-3.
15-30 cm long, 0.8-3.5 cm wide;
branches straight, appressed to ascending, lower branches 3-9 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.
appressed to the branches.
subequal, 9-11.5 mm long, 1-1.4 mm wide;
florets 5.9-8.5 mm long, 0.9-1.2 mm thick, fusiform, terete;
calluses 0.3-1 mm, blunt;
lemmas evenly hairy, hairs at midlength 0.3-0.8 mm, apical hairs to 1.5 mm;
awns 20-32 mm, persistent, twice-geniculate, scabridulous to scabrous, scabrules to about 0.1 mm, longest on the middle segment, terminal segment straight;
paleas 3.7-5.6 mm, 2/3 - 3/4 as long as the lemmas, hairy, hairs about 0.5 mm, not exceeding the apices, veins terminating below the apices, apices rounded;
anthers 4-5 mm, dehiscent, penicillate.
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.
5-6 mm.
about 4 mm, fusiform.
sheaths mostly glabrous, margins usually ciliate distaily;
collars hairy, those of the flag leaves densely hairy, hairs 0.5-2 mm, sides glabrous;
basal ligules 1-2 mm;
upper ligules to 4 mm, truncate, rounded, or obtuse, glabrous;
blades 6-10 mm wide, glabrous, abaxial surfaces smooth, adaxial surfaces prominently ribbed, ribs scabrous.
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.
= 64.
= 44, 46.
Achnatherum robustum
Achnatherum eminens
Achnatherum robustum grows on dry plains and hills, in open woods and forest clearings, and along roadsides, from Wyoming through Colorado to Arizona, New Mexico, and northern Mexico. Records from Kansas represent recent introductions; it is not clear whether the species has persisted there. Achnatherum robustum is sometimes confused with A. nelsonii subsp. dorei and Nassella viridula; it differs from both in the densely hairy collars of its flag leaves. Although not widely available, it has potential as an ornamental grass, particularly in arid regions with cold winters.
The English-language name refers to the effect some samples, particularly those from the Sacramento and Sierra Blanca mountains, New Mexico, have on livestock, especially horses and cattle. "Mildly poisoned animals are dejected, inactive, and withdrawn; severely poisoned animals lie on their sides in a profound slumber" (Cheeke and Shull 1985). The active ingredient is diacetone alcohol (Epstein et al 1964).
(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.)
KS Wildflowers
WildflowerSearch
iNaturalist
USDA Plants Database
