Achnatherum robustum

(Vasey) Barkworth
Common names: Sleepygrass
Synonyms: Stipa vaseyi Stipa robusta
Treatment appears in FNA Volume 24. Treatment on page 129.
Please click on the illustration for a higher resolution version.
Illustrator: Cindy Roché

Copyright: Utah State University

Plants cespitose, not rhizomatous. Culms 100-230 cm tall, 2-4.5 mm thick, mostly glabrous, often pubescent below the nodes, the pubescence antrorse or retrorse; nodes 4-5. Basal 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. Panicles 15-30 cm long, 0.8-3.5 cm wide; branches straight, appressed to ascending, lower branches 3-9 cm. Spikelets appressed to the branches. Glumes 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. Caryopses 5-6 mm. 2n = 64.

Distribution

Colo., N.Mex., Tex., Nebr., Kans., Ariz., Wyo., S.Dak.

Discussion

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 "Mildly poisoned animals are dejected, inactive, and withdrawn; severely poisoned animals lie on their sides in a profound slumber" (Cheeke and Shull 1985).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).

Selected References

None.

Lower Taxa

None.

No values specified."decumbent" is not a number."prolonged" is not a number.

... more about "Achnatherum robustum"
membranous +  and scarious +
penicillate +
0.4 cm4 mm <br />0.004 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
awned +, bifid +, bilobed +  and entire +
Rounded (?) +  and Acute (?) +
0 cm0 mm <br />0 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
Mary E. Barkworth +
(Vasey) Barkworth +
1 (?) +  and 3 (?) +
flexuous +
subterminal +  and eccentric +
usually scabrous +  and scabridulous +
not once-geniculate +
2 cm20 mm <br />0.02 m <br /> (3.2 cm32 mm <br />0.032 m <br />) +
keeled +  and rounded +
pseudopetiolate +  and branching +
intravaginal +, extravaginal +, branching +  and basal +
swelling +
not evident +
involute +, convolute +  and flat +
6mm;10mm +
appressed;ascending +
spikelike +
well-developed +
0.03 cm0.3 mm <br />3.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
Sleepygrass +
branching +  and not branching +
perennial +  and annual +
100 cm1,000 mm <br />1 m <br /> (230 cm2,300 mm <br />2.3 m <br />) +
retrorse +, antrorse +  and pubescence +
intravaginal +  and basal +
pubescent +  and glabrous +
10 cm100 mm <br />0.1 m <br /> (250 cm2,500 mm <br />2.5 m <br />) +
not woody +
0.2 cm2 mm <br />0.002 m <br /> (0.45 cm4.5 mm <br />0.0045 m <br />) +
Colo. +, N.Mex. +, Tex. +, Nebr. +, Kans. +, Ariz. +, Wyo. +  and S.Dak. +
1/5 +  and 1/3 +
liquid +, soft +  and hard +
capillary +
pistillate +  and staminate +
0.59 cm5.9 mm <br />0.0059 m <br /> (0.85 cm8.5 mm <br />0.0085 m <br />) +
sometimes longer +
terete +  and fusiform +
9mm +  and 11.5mm +
subtending +
obtuse +, acute +  and acuminate +
subequal +
membranous +
1mm +  and 1.4mm +
divergent +  and distributed +
uncinate +
0.5 cm5 mm <br />0.005 m <br /> (0.05 cm0.5 mm <br />5.0e-4 m <br />) +
solid +  and hollow +
basally concentrated +  and evenly distributed +
0 cm0 mm <br />0 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
ovate +, rectangular +  and lanceolate +
stiffly membranous +  and coriaceous +
pubescent +  and glabrous +
membranous +
membranous +
inconspicuous +
not lobed +
3 cm30 mm <br />0.03 m <br /> (9 cm90 mm <br />0.09 m <br />) +
concealed +  and prominent +
4 +  and 5 +
2 +  and 1 +
pubescent +  and glabrous +
well-developed +
2/3 +  and 3/4 +
not keeled +
reduced +
0.37 cm3.7 mm <br />0.0037 m <br /> (0.56 cm5.6 mm <br />0.0056 m <br />) +
15cm +  and 30cm +
0.8 cm8 mm <br />0.008 m <br /> (3.5 cm35 mm <br />0.035 m <br />) +
dry +  and fleshy +
not prolonged +
1 +  and 60 +
unisexual +  and bisexual +
laterally compressed +  and terete +
1 (?) +  and 3 (?) +
simple +  and compound +
Stipa vaseyi +  and Stipa robusta +
Achnatherum robustum +
Achnatherum +
species +
membranous +
inconspicuous +
0.1 cm1 mm <br />0.001 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
plant +  and cespitose +
aquatic +  and terrestrial +