Achnatherum richardsonii

(Link) Barkworth
Common names: Richardson's needlegrass
Synonyms: Stipa richardsonii
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 tightly cespitose, not rhizomatous. Culms 30-100 cm tall, 1-1.5 mm thick, glabrous; nodes usually 3. Basal sheaths glabrous, margins ciliolate; collars glabrous, without tufts of hair on the sides; ligules 0.1-0.5 mm, truncate, ciliolate; blades 0.8-3 mm wide, convolute when dry, abaxial surfaces scabridulous, adaxial surfaces glabrous. Panicles 7-25 cm long, 7-15 cm wide; branches divergent, flexuous, longest branches 7-10 cm, with the spikelets confined to the distal 1/4. Spikelets pendulous. Lower glumes 7.5-11 mm long, 0.9-1.2 mm wide; upper glumes 2-3 mm shorter; florets 5-6 mm long, 0.6-0.9 mm thick, fusiform, terete; calluses 0.4-0.7 mm, blunt; lemmas evenly hairy on the lower portion, often glabrate distally, body and apical hairs 0.2-0.5 mm, apical lobes not or scarcely developed, to 0.1 mm; awns 15-25 mm, persistent, twice-geniculate, first 2 segments strigulose, hairs about 0.1 mm, termi¬nal segment straight; paleas 2.2-3.6 mm, 1/2 - 3/5 as long as the lemmas, pubescent, hairs not exceeding the apices, apices rounded; anthers 2.5-3 mm, dehiscent, penicillate, hairs 0.1-0.5 mm. Caryopses 3-4 mm, fusiform. 2n = 44.

Distribution

Colo., Wash., Alaska, Mont., Alta., B.C., Man., Sask., Yukon, Idaho, Wyo., S.Dak.

Discussion

Achnatherum richardsonii grows in open woodlands and grasslands,often on sand or gravel, from the Yukon Territory to Washington and Manitoba, and south in the Rocky Mountains through Montana and Wyoming to western South Dakota and northern Colorado. Its elevation range is 1000-3100 m. It is readily recognized by its combination of flexuous panicle branches, drooping spikelets, and straight distal awn segments. Scagel and Maze (1984) concluded that putative hybrids between A. richardsonii and A. nelsonii subsp. dorei were merely large plants of subsp. dorei that varied in the direction of A. richardsonii.

Selected References

None.

Lower Taxa

None.

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

... more about "Achnatherum richardsonii"
membranous +  and scarious +
penicillate +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
awned +, bifid +, bilobed +  and entire +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.05 cm0.5 mm <br />5.0e-4 m <br />) +
Mary E. Barkworth +
(Link) Barkworth +
1 (?) +  and 3 (?) +
flexuous +
subterminal +  and eccentric +
usually scabrous +  and scabridulous +
not once-geniculate +
1.5 cm15 mm <br />0.015 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
keeled +  and rounded +
pseudopetiolate +  and branching +
intravaginal +, extravaginal +, branching +  and basal +
swelling +
not evident +
involute +, convolute +  and flat +
0.8mm;3mm +
spikelike +
well-developed +
0.04 cm0.4 mm <br />4.0e-4 m <br /> (0.07 cm0.7 mm <br />7.0e-4 m <br />) +
Richardson's needlegrass +
branching +  and not branching +
perennial +  and annual +
30 cm300 mm <br />0.3 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 +
0.1 cm1 mm <br />0.001 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
Colo. +, Wash. +, Alaska +, Mont. +, Alta. +, B.C. +, Man. +, Sask. +, Yukon +, Idaho +, Wyo. +  and S.Dak. +
1/5 +  and 1/3 +
liquid +, soft +  and hard +
capillary +
pistillate +  and staminate +
0.5 cm5 mm <br />0.005 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
sometimes longer +
terete +  and fusiform +
1-10-veined +
subtending +
obtuse +, acute +  and acuminate +
membranous +
divergent +  and distributed +
uncinate +
0.01 cm0.1 mm <br />1.0e-4 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 />) +
glabrate +  and hairy +
ovate +, rectangular +  and lanceolate +
stiffly membranous +  and coriaceous +
0.01 cm0.1 mm <br />1.0e-4 m <br /> (0.05 cm0.5 mm <br />5.0e-4 m <br />) +
membranous +
membranous +
inconspicuous +
not lobed +
7 cm70 mm <br />0.07 m <br /> (10 cm100 mm <br />0.1 m <br />) +
0.75 cm7.5 mm <br />0.0075 m <br /> (1.1 cm11 mm <br />0.011 m <br />) +
0.9mm +  and 1.2mm +
concealed +  and prominent +
2 +  and 1 +
pubescent +  and glabrous +
well-developed +
1/2 +  and 3/5 +
not keeled +
reduced +
0.22 cm2.2 mm <br />0.0022 m <br /> (0.36 cm3.6 mm <br />0.0036 m <br />) +
7cm +  and 25cm +
7 cm70 mm <br />0.07 m <br /> (15 cm150 mm <br />0.15 m <br />) +
dry +  and fleshy +
not prolonged +
1 +  and 60 +
unisexual +  and bisexual +
laterally compressed +  and terete +
1 (?) +  and 3 (?) +
simple +  and compound +
Stipa richardsonii +
Achnatherum richardsonii +
Achnatherum +
species +
membranous +
0.2 cm2 mm <br />0.002 m <br /> (0.3 cm3 mm <br />0.003 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 +