Achnatherum robustum
Achnatherum perplexum
sleepy grass
New Mexico needlegrass, perplexing 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.
35-90 cm tall, 0.7-2.2 mm thick, lower internodes glabrous, puberulent to 5 mm below the nodes;
nodes 2-3.
15-30 cm long, 0.8-3.5 cm wide;
branches straight, appressed to ascending, lower branches 3-9 cm.
10-25 cm long, 0.5-1.5 cm wide;
branches ascending to appressed, straight.
appressed to the branches.
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.
unequal;
lower glumes 10-15 mm long, 0.5-1.1 mm wide, exceeding the upper glumes by 1-3(4) mm;
florets 5.5-11 mm long, 0.7-1 mm thick, fusiform, terete, widest at or below midlength;
calluses 0.4-0.6 mm, blunt;
lemmas evenly hairy, hairs at midlength about 1 mm, apical hairs 1-2 mm, ascending to divergent, apical lobes 0.2-0.5 mm, membranous, flexible;
awns 10-19 mm, persistent, once(twice)-geniculate, basal segments scabrous, terminal segments straight;
paleas 2.8-5.6 mm, 1/2 -2/3 as long as the lemmas, hairy, hairs not or scarcely exceeding the apices, veins terminating at or before the apices, apices acute to rounded;
anthers 2.5-4 mm, dehiscent, not penicillate.
5-6 mm.
3-6 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, margins ciliolate distally;
collars glabrous, including the sides;
basal ligules 0.2-0.5 mm, truncate, ciliolate, cilia to 0.1 mm;
upper ligules 0.2-3.5 mm, rounded to acute;
blades to 30 cm long, 1-3 mm wide.
= 64.
= unknown.
Achnatherum robustum
Achnatherum perplexum
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 perplexum grows on slopes in pinyon-pine associations of the southwestern United States and adjacent Mexico, at 1500-1700 m. It flowers in late summer to early fall. It has generally been confused with A. scribneri, A. nelsonii, and A. lobatum. It differs from A. scribneri in the glabrous collar margins of its basal leaves and its blunt calluses; from A. nelsonii and A. lettermanii in its unequal glumes; from A. lettermanii in its relatively short paleas; and from A. lobatum in its shorter lemma lobes and ascending to divergent apical lemma hairs.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
KS Wildflowers
WildflowerSearch
iNaturalist
USDA Plants Database
