Achnatherum robustum
Achnatherum stillmanii
sleepy grass
Stillman's needlegrass, Stuxman's 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.
60-150 cm tall, 2-5 mm thick, often geniculate at the lowest node, mostly glabrous;
nodes 2-3, often puberulent.
15-30 cm long, 0.8-3.5 cm wide;
branches straight, appressed to ascending, lower branches 3-9 cm.
10-24 cm long, 1.5-3 cm wide, contracted;
branches straight, appressed to strongly ascending, lower branches 2.5-3.5 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.
subequal, 14-16 mm;
lower glumes 1-3-veined;
upper glumes 0.6-1.5 mm wide, 3-5-veined;
florets 8-10 mm, fusiform;
calluses 0.5-1.2 mm, rounded;
lemmas evenly hairy, hairs about 0.5 mm, apical hairs similar in length, apices 2-lobed, lobes 1-3 mm, narrow;
awns 18-25 mm, persistent, scabrous, once- or twice-geniculate, terminal segment straight;
paleas as long as or slightly longer than the lemmas, hairy, hairs about 0.5 mm, veins prolonged, reaching almost to the tips of the lemma lobes;
anthers 4-6 mm, penicillate, dehiscent.
5-6 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, sometimes ciliate distally, intact at maturity;
collars glabrous or pubescent, often with hairs at the sides, hairs shorter than 0.5 mm;
basal ligules 0.2-0.5 mm, membranous, truncate, ciliate, cilia 0.2-0.3 mm;
upper ligules shorter than the basal ligules;
blades 3-7 mm wide, lax.
= 64.
= unknown.
Achnatherum robustum
Achnatherum stillmanii
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 stillmanii grows at scattered locations in coniferous forests in northern California, at 900-1500 m, possibly being edaphically restricted. Its combination of large size, long, narrow lemma lobes, and paleal morphology distinguish A. stillmanii from all other North American species of Achnatherum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
KS Wildflowers
WildflowerSearch
iNaturalist
USDA Plants Database
CA
