Achnatherum occidentale subsp. occidentale

Common names: Western needlegrass
Endemic
Treatment appears in FNA Volume 24. Treatment on page 123.
Please click on the illustration for a higher resolution version.
Illustrator: Cindy Roché

Copyright: Utah State University

Culms 14-50 cm tall, 0.3-1 mm thick, internodes glabrous. Basal sheaths mostly glabrous, often ciliate or sparsely tomentose at the throat; collars usually without tufts of hair at the sides; blades 0.3-2 mm wide when flat, usually convolute and 0.1-0.2 mm in diameter. Panicles 5-20 cm; longest branches 1.5-4 cm. Glumes often purplish; lemmas with apical pubescence similar in length to the basal awn pubescence; awns 15-42 mm, first 2 segments always pilose, terminal segment usually pilose, hairs becoming shorter distally, occasionally scabridulous or smooth.

Discussion

Achnatherum occidentale subsp. occidentale grows above 2400 m, primarily in California. It differs from A. occidentale subsp. pubescens in having culms that are glabrous throughout and awns with terminal segments that are usually pilose. One specimen from Idaho has been seen; it has the palea/lemma ratio of subsp. californicum but the pilose terminal awn segments, slender habit, and purplish coloration of subsp. occidentale.

Selected References

None.

Lower Taxa

None.

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

membranous +  and scarious +
not penicillate +
0.25 cm2.5 mm <br />0.0025 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 +
(Thurb.) Barkworth +
1 (?) +  and 3 (?) +
flexuous +
subterminal +  and eccentric +
usually scabrous +  and scabridulous +
not once-geniculate +
1.5 cm15 mm <br />0.015 m <br /> (4.2 cm42 mm <br />0.042 m <br />) +
keeled +  and rounded +
tomentose +, ciliate +  and glabrous +
pseudopetiolate +  and branching +
intravaginal +, extravaginal +, branching +  and basal +
swelling +
straight +
0.01 cm0.1 mm <br />1.0e-4 m <br /> (0.02 cm0.2 mm <br />2.0e-4 m <br />) +
not evident +
convolute +  and flat +
0.3mm;2mm +
spikelike +
well-developed +
0.08 cm0.8 mm <br />8.0e-4 m <br /> (0.12 cm1.2 mm <br />0.0012 m <br />) +
Western needlegrass +
branching +  and not branching +
perennial +  and annual +
14 cm140 mm <br />0.14 m <br /> (50 cm500 mm <br />0.5 m <br />) +
intravaginal +  and basal +
10 cm100 mm <br />0.1 m <br /> (250 cm2,500 mm <br />2.5 m <br />) +
not woody +
0.03 cm0.3 mm <br />3.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
Utah +, Wash. +, Colo. +, Mont. +, Alta. +, B.C. +, Idaho +, Calif. +, Wyo. +, Ariz. +, Nev. +  and Oreg. +
1/5 +  and 1/3 +
liquid +, soft +  and hard +
capillary +
pistillate +  and staminate +
0.55 cm5.5 mm <br />0.0055 m <br /> (0.75 cm7.5 mm <br />0.0075 m <br />) +
sometimes longer +
terete +  and fusiform +
9mm +  and 15mm +
subtending +
obtuse +, acute +  and acuminate +
subequal +
membranous +
0.6mm +  and 0.9mm +
divergent +  and distributed +
smooth +  and scabridulous +
uncinate +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.15 cm1.5 mm <br />0.0015 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 />) +
glabrous +  and hairy +
ovate +, rectangular +  and lanceolate +
stiffly membranous +  and coriaceous +
pubescent +  and glabrous +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
membranous +
membranous +
inconspicuous +
not lobed +
1.5 cm15 mm <br />0.015 m <br /> (4 cm40 mm <br />0.04 m <br />) +
concealed +  and prominent +
pubescent +  and glabrous +
2 +  and 4 +
2 +  and 1 +
pubescent +  and glabrous +
well-developed +
2/5 +  and 3/5 +
not keeled +
reduced +
0.22 cm2.2 mm <br />0.0022 m <br /> (0.35 cm3.5 mm <br />0.0035 m <br />) +
5cm +  and 30cm +
5 cm50 mm <br />0.05 m <br /> (20 cm200 mm <br />0.2 m <br />) +
0.5 cm5 mm <br />0.005 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
dry +  and fleshy +
not prolonged +
1 +  and 60 +
unisexual +  and bisexual +
laterally compressed +  and terete +
1 (?) +  and 3 (?) +
simple +  and compound +
Stipa occidentalis +  and Stipa occidentalis var. montana +
Achnatherum occidentale subsp. occidentale +
Achnatherum occidentale +
subspecies +
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 +