Achnatherum robustum
Achnatherum curvifolium
sleepy grass
curlyleaf needlegrass, Guadalupe ricegrass
100-230 cm tall, 2-4.5 mm thick, mostly glabrous, often pubescent below the nodes, the pubescence antrorse or retrorse;
nodes 4-5.
25-55 cm tall, 0.7-1 mm thick, glabrous;
nodes 3.
15-30 cm long, 0.8-3.5 cm wide;
branches straight, appressed to ascending, lower branches 3-9 cm.
7-11 cm long, 1-2 cm wide;
branches appressed to strongly ascending, longest branches 3-4 cm.
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, 10-14 mm long, 0.7-0.9 mm wide;
florets 6-8 mm long, 0.4-0.8 mm thick, fusiform, terete;
calluses 1-1.5 mm, sharp;
lemmas evenly hairy, hairs at midlength 0.3-1 mm, apical hairs 1-1.5 mm, apical lobes not developed;
awns 22-38 mm, once-geniculate, first segment pubescent, hairs 1-2 mm, gradually decreasing in length distally;
paleas 2-2.3 mm, 1/4-1/3 as long as the lemmas, glabrous;
anthers about 3.5 mm, dehiscent, not penicillate.
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 usually puberulent, hairs 0.1-0.2 mm, sometimes densely tomentose at the base, brown to gray-brown when old;
collars glabrous, sometimes with tufts of hair on the sides, hairs to 0.5 mm;
ligules truncate, pubescent, hairs about 0.1;
basal ligules about 0.3 mm, upper ligules to 0.6 mm;
blades normally valvate to involute, about 0.5 mm in diameter, strongly arcuate, abaxial surfaces pubescent near the base, glabrous and smooth distally, adaxial surfaces densely hairy, hairs to 0.2 mm.
= 64.
= 44.
Achnatherum robustum
Achnatherum curvifolium
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 curvifolium grows on cliffs and in disturbed, rocky, limestone habitats. It is known from relatively few locations in the Flora region; it is more common in northern Mexico. It is most readily distinguished from other species of Achnatherum in the Flora region by its combination of curly leaves and hairy awns.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
KS Wildflowers
WildflowerSearch
iNaturalist
USDA Plants Database
