Achnatherum webberi

(Thurb.) Barkworth
Common names: Webber's needlegrass
Endemic
Synonyms: Stipa webberi Oryzopsis webberi
Treatment appears in FNA Volume 24. Treatment on page 137.
Please click on the illustration for a higher resolution version.
Illustrator: Cindy Roché

Copyright: Utah State University

Plants tightly cespitose, not rhizomatous. Culms 12-35 cm tall, 0.4-0.7 mm thick, smooth or antrorsely scabridulous; nodes 2-3. Basal sheaths glabrous, smooth or scabridulous; collars glabrous, without tufts of hair on the sides; basal ligules 0.1-1 mm, truncate to rounded; upper ligules 1-2 mm, acute; blades 0.5-1.5 mm wide when flat, usually folded to involute and about 0.5 mm in diameter, stiff, abaxial surfaces smooth or scabrous, adaxial surfaces scabrous. Panicles 2.5-7 cm long, 0.5-2 cm wide, contracted; branches appressed, longest branches 1-2 cm. Glumes subequal, 6-10 mm long, 0.6-0.9 mm wide, lanceolate, not saccate; florets 4.5-6 mm long, 0.7-1 mm thick, fusiform, terete; calluses 0.3-0.8 mm, blunt; lemmas evenly and densely pilose, hairs 2.5-3.5 mm, apical lobes 0.6-1.9 mm, membranous; awns 4-11 mm, readily deciduous, straight to once-geniculate, scabrous; paleas 4-5.6 mm, from as long as to slightly longer than the lemmas; anthers 1.6-2 mm, dehiscent, not penicillate. Caryopses 3.5-4.5 mm, fusiform. 2n = 32.

Distribution

Colo., Utah, Calif., Oreg., Idaho, Nev., S.Dak.

Discussion

Achnatherum webberi grows in dry, open flats and on rocky slopes, often with sagebrush, at 1500-2500 m. It grows at scattered locations from Oregon and Idaho to California and Nevada. It differs from A. hymenoides in its cylindrical floret and non-saccate glumes, and from A. pinetorum and A. parishii subsp. parishii in its shorter, deciduous awns. It also has narrower blades than A. parishii subsp. depauperatum.

Selected References

None.

Lower Taxa

None.

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

... more about "Achnatherum webberi"
membranous +  and scarious +
not penicillate +
0.16 cm1.6 mm <br />0.0016 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
awned +, bifid +, bilobed +  and entire +
Rounded (?) +  and Acute (?) +
0 cm0 mm <br />0 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
Mary E. Barkworth +
(Thurb.) Barkworth +
1 (?) +  and 3 (?) +
straight +
subterminal +  and eccentric +
usually scabrous +  and scabridulous +
once-geniculate +
0.4 cm4 mm <br />0.004 m <br /> (1.1 cm11 mm <br />0.011 m <br />) +
keeled +  and rounded +
pseudopetiolate +  and branching +
intravaginal +, extravaginal +, branching +  and basal +
swelling +
not evident +
usually folded +  and involute +
0.5 cm5 mm <br />0.005 m <br /> (?) +
0.5mm;1.5mm +
flexuous +  and straight +
spikelike +
well-developed +
0.03 cm0.3 mm <br />3.0e-4 m <br /> (0.08 cm0.8 mm <br />8.0e-4 m <br />) +
Webber's needlegrass +
branching +  and not branching +
perennial +  and annual +
12 cm120 mm <br />0.12 m <br /> (35 cm350 mm <br />0.35 m <br />) +
intravaginal +  and basal +
10 cm100 mm <br />0.1 m <br /> (250 cm2,500 mm <br />2.5 m <br />) +
not woody +
0.04 cm0.4 mm <br />4.0e-4 m <br /> (0.07 cm0.7 mm <br />7.0e-4 m <br />) +
Colo. +, Utah +, Calif. +, Oreg. +, Idaho +, Nev. +  and S.Dak. +
1/5 +  and 1/3 +
liquid +, soft +  and hard +
capillary +
pistillate +  and staminate +
0.45 cm4.5 mm <br />0.0045 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
sometimes longer +
terete +  and fusiform +
6mm +  and 10mm +
subtending +
lanceolate +
subequal +
membranous +
0.6mm +  and 0.9mm +
divergent +  and distributed +
uncinate +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.35 cm3.5 mm <br />0.0035 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 +
1 cm10 mm <br />0.01 m <br /> (2 cm20 mm <br />0.02 m <br />) +
concealed +  and prominent +
2 +  and 3 +
2 +  and 1 +
pubescent +  and glabrous +
well-developed +
not keeled +
reduced +
0.4 cm4 mm <br />0.004 m <br /> (0.56 cm5.6 mm <br />0.0056 m <br />) +
2.5cm +  and 7cm +
0.5 cm5 mm <br />0.005 m <br /> (2 cm20 mm <br />0.02 m <br />) +
dry +  and fleshy +
not prolonged +
1 +  and 60 +
unisexual +  and bisexual +
laterally compressed +  and terete +
1 (?) +  and 3 (?) +
simple +  and compound +
Stipa webberi +  and Oryzopsis webberi +
Achnatherum webberi +
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 +