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.

Mary E. Barkworth +
(Thurb.) Barkworth +
Western needlegrass +
Utah +, Wash. +, Colo. +, Mont. +, Alta. +, B.C. +, Idaho +, Calif. +, Wyo. +, Ariz. +, Nev. +  and Oreg. +
Stipa occidentalis +  and Stipa occidentalis var. montana +
Achnatherum occidentale subsp. occidentale +
Achnatherum occidentale +
subspecies +