Achnatherum richardsonii
Achnatherum coronatum
Richardson needlegrass, Richardson's needlegrass, Richardson's rice grass, spreading needlegrass
crested needlegrass, giant ricegrass
30-100 cm tall, 1-1.5 mm thick, glabrous;
nodes usually 3.
55-210 cm tall, 3-6 mm thick, internodes usually glabrous, lower internodes sometimes puberulent;
nodes 1-2, glabrous.
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.
15-60 cm long, 2-4 cm wide;
branches widely spreading to ascending, longest branches 4-13 cm.
pendulous.
lanceolate, glabrous, tapering to awnlike apices;
lower glumes 16-21 mm long, 1-1.3 mm wide, midveins scabrous;
upper glumes 11-18 mm;
florets 6.5-10 mm long, about 1 mm thick, fusiform, terete;
calluses 0.5-2 mm, blunt to acute;
lemmas densely hairy, hairs at midlength 1.5-4 mm, apical hairs 2-5 mm;
awns 25-45 mm, persistent, twice-geniculate, all segments scabrous, terminal segment straight;
paleas 3.5-5.5 mm, 3/5 – 9/10 as long as the lemmas, sparsely hairy between the veins, apices flat, rounded;
anthers 3-4 mm, dehiscent, not penicillate.
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, terminal 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.
3-4 mm, fusiform.
5-7 mm, fusiform.
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.
sheaths mostly glabrous, often puberulent on the lower portion, flat, ribbonlike with age, margins hairy distally, hairs 1-2.5 mm;
collars mostly glabrous;
ligules 0.4-1.6(3) mm, truncate to slightly rounded, abaxial surfaces pubescent, ciliate, cilia about 0.5 mm;
blades usually flat, 2.5-7 mm wide, both surfaces scabrous.
= 44.
= 40.
Achnatherum richardsonii
Achnatherum coronatum
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Achnatherum coronatum grows on gravel and on rocky slopes, mostly in chaparral associations of the Coast Range from Monterey County, California, to Baja California, Mexico. It is similar in size to A. diegoense, but differs in its mostly glabrous internodes and longer paleas. It differs from A. parishii, an inland species, in its twice-geniculate awns, more robust habit, and more sparsely pubescent paleas. Occasional plants combine the characteristics of both species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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