Achnatherum robustum
Achnatherum lobatum
sleepy grass
littleawn needlegrass, lobed 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.
40-100 cm tall, 0.6-2.6 mm thick, glabrous or sparsely pubescent to 5 mm below the lower nodes;
nodes 4.
15-30 cm long, 0.8-3.5 cm wide;
branches straight, appressed to ascending, lower branches 3-9 cm.
12-28 cm long, 0.5-1.5 cm wide;
branches ascending to appressed, straight, longest branches 3-6 cm.
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 9.5-12.5 mm long, 0.8-1.2 mm wide, 3(5, 7)-veined, apices straight to somewhat recurved;
upper glumes 2-3.5 mm shorter, 3-veined;
florets 5.5-7.5 mm long, 0.6-1.1 mm thick, terete, widest about midlength;
calluses 0.3-0.5 mm, blunt;
lemmas evenly hairy, hairs at midlength 0.7-1.2 mm, fusiform, terete, apical hairs 1.3-2.2 mm, erect, usually less than 1 mm longer than those at midlength, apical lobes 0.5-1.2 mm, membranous, flexible;
awns 10-22 mm, persistent, once- or twice-geniculate, scabrous, terminal segments straight;
paleas 3-4.3 mm, 3/5 – 3/4 as long as the lemmas, pubescent, hairs exceeding the apices, veins terminating below the apices, apices flat, rounded;
anthers 3-4 mm, dehiscent, sparsely penicillate, hairs about 0.1 mm.
5-6 mm.
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 becoming flat and papery in age, margins sometimes ciliate distally, cilia to 0.5 mm;
collars, including the sides, glabrous or sparsely pubescent, collars of the flag leaves glabrous;
basal ligules 0.2-1.3 mm, membranous, truncate, erose to ciliate, cilia about 0.05 mm;
upper ligules 0.3-1 mm;
blades 1-4 mm wide, abaxial surfaces smooth, adaxial surfaces scabrous.
= 64.
= unknown.
Achnatherum robustum
Achnatherum lobatum
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 lobatum grows on rocky, open slopes in pinyon-pine and white fir associations of southern Arizona, New Mexico, Texas, and northern Mexico, at 2100-2800 m. It flowers from mid- to late summer.
Achnatherum lobatum is similar to A. scribneri and A. perplexum. It differs from A. scribneri in its shorter apical lemma hairs and blunt calluses, and from A. perplexum in having longer lemma lobes and erect apical hairs.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
KS Wildflowers
WildflowerSearch
iNaturalist
USDA Plants Database
