Achnatherum eminens

(Cav.) Barkworth
Common names: Southwestern needlegrass
Synonyms: Stipa eminens
Treatment appears in FNA Volume 24. Treatment on page 133.
Please click on the illustration for a higher resolution version.
Illustrator: Cindy Roché

Copyright: Utah State University

Plants cespitose, shortly rhizomatous, bases knotty. Culms 50-100 cm tall, 0.8-1.5 mm thick, glabrous; nodes 2-3. Basal sheaths mostly glabrous, ciliate on the margins; collars glabrous on the back, usually with tufts of hair on the sides, hairs about 0.8 mm; basal ligules 0.8-1.6 mm, membranous, glabrous, rounded to acute; upper ligules to 4.5 mm, acute; blades 0.7-3.5 mm wide, abaxial surfaces smooth to scabridulous, adaxial surfaces prominently ribbed, scabridulous or sparsely to densely pubescent, hairs about 0.1 mm. Panicles 20-55 cm long, 3-8 cm wide, open, often enclosed to midlength at anthesis; lower branches 5-8 cm, ascending to divergent, flexuous. Lower glumes 5-12 mm long, 0.5-0.7 mm wide, 3-5-veined; upper glumes 1-4 mm shorter, 3-veined; florets 4-7.5 mm long, 0.5-0.9 mm thick, fusiform, terete; calluses 1-2 mm, sharp; lemmas evenly hairy, hairs 0.4-0.8 mm throughout, apical lobes not present; awns 35-70 mm, persistent, twice-geniculate, first 2 segments scabrous, terminal segment flexuous; paleas 1-2 mm, 1/3 – 1/2 as long as the lemmas, sparsely to moderately pubescent, apices rounded, flat; anthers 3-3.5 mm, dehiscent, a few penicillate, hairs about 0.3 mm. Caryopses about 4 mm, fusiform. 2n = 44, 46.

Discussion

Achnatherum eminens grows on dry, rocky slopes and valleys in the mountains of the southwestern United States, primarily in desert scrub, at 600-2600 m. Its range extends into Mexico. It is easy to recognize because of its open panicle, flexuous branches, and flexuous awns. It is superficially similar to Nassella cernua, but differs in its longer, glabrous ligules, not or weakly overlapping lemma margins, pubescent paleas, and geographic distribution.

Selected References

None.

Lower Taxa

None.

"decumbent" is not a number."prolonged" is not a number.

... more about "Achnatherum eminens"
smooth +  and scabridulous +
membranous +  and scarious +
penicillate +
0.3 cm3 mm <br />0.003 m <br /> (0.35 cm3.5 mm <br />0.0035 m <br />) +
awned +, bifid +, bilobed +  and entire +
0 cm0 mm <br />0 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
Mary E. Barkworth +
(Cav.) Barkworth +
1 (?) +  and 3 (?) +
flexuous +
subterminal +  and eccentric +
usually scabrous +  and scabridulous +
not once-geniculate +
3.5 cm35 mm <br />0.035 m <br /> (7 cm70 mm <br />0.07 m <br />) +
keeled +  and rounded +
pseudopetiolate +  and branching +
intravaginal +, extravaginal +, branching +  and basal +
swelling +
not evident +
involute +, convolute +  and flat +
0.7mm;3.5mm +
flexuous +  and straight +
spikelike +
well-developed +
0.1 cm1 mm <br />0.001 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
Southwestern needlegrass +
branching +  and not branching +
perennial +  and annual +
50 cm500 mm <br />0.5 m <br /> (100 cm1,000 mm <br />1 m <br />) +
intravaginal +  and basal +
10 cm100 mm <br />0.1 m <br /> (250 cm2,500 mm <br />2.5 m <br />) +
not woody +
0.08 cm0.8 mm <br />8.0e-4 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
Ariz. +, N.Mex. +  and Tex. +
1/5 +  and 1/3 +
liquid +, soft +  and hard +
capillary +
pistillate +  and staminate +
0.4 cm4 mm <br />0.004 m <br /> (0.75 cm7.5 mm <br />0.0075 m <br />) +
sometimes longer +
terete +  and fusiform +
1-10-veined +
subtending +
obtuse +, acute +  and acuminate +
membranous +
divergent +  and distributed +
uncinate +
0.3 cm3 mm <br />0.003 m <br /> (0.04 cm0.4 mm <br />4.0e-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 +
5 cm50 mm <br />0.05 m <br /> (8 cm80 mm <br />0.08 m <br />) +
0.5 cm5 mm <br />0.005 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
0.5mm +  and 0.7mm +
concealed +  and prominent +
2 +  and 3 +
2 +  and 1 +
pubescent +  and glabrous +
well-developed +
1/3 +  and 1/2 +
not keeled +
reduced +
0.1 cm1 mm <br />0.001 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
20cm +  and 55cm +
enclosed +  and midlength +
3 cm30 mm <br />0.03 m <br /> (8 cm80 mm <br />0.08 m <br />) +
dry +  and fleshy +
not prolonged +
1 +  and 60 +
unisexual +  and bisexual +
laterally compressed +  and terete +
1 (?) +  and 3 (?) +
simple +  and compound +
Stipa eminens +
Achnatherum eminens +
Achnatherum +
species +
membranous +
0.1 cm1 mm <br />0.001 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
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 +