Scientific Name
Achnatherum lettermanii (Vasey) Barkworth (Synonyms: Stipa lettermanii)
Common Name(s)
Letterman's needlegrass
Tribe / Family Name
Stipeae
Flowering Period
June to August
Symbol
ACLE9
Description
Letterman’s needlegrass is a native cool-season perennial bunchgrass that reproduces from seeds and tillers. Culms range from 15–90 cm in height. Its inflorescence is a narrow panicle 7–19 cm long with erect branches and few spikelets. Spikelets are appressed to the branches, 1-flowered, and awned (the lemma awns 12–25 mm long, twice geniculate, loosely twisted and scabrous along the first two segments, straight and glabrous along the terminal segment, and persistent). Ligules are usually up to 2 mm long, membranous, obtuse to truncate, without tufts of hair on sides, and decurrent.
General Info
Letterman’s needlegrass can be found along rocky ridges, in sagebrush steppe, valleys, meadows, and open forests and woodlands.
Similar Species
Letterman’s needlegrass looks similar to other needlegrass (Achnatherum) species, especially Columbia needlegrass (Achnatherum nelsonii ssp. nelsonii). Although both species have awns that are scabrous along the first two segments, they can be separated by observing their heights, leaves, inflorescences, and awns. Letterman’s needlegrass is usually a less robust plant with narrower leaves, shorter inflorescences, and smaller awns, and Columbia needlegrass is usually a more robust plant with wider leaves, bigger inflorescences, and longer awns. Also, Letterman’s needlegrass has apical hairs on the paleae that generally exceed the apices, and Columbia needlegrass has apical hairs on the paleae that are generally not exceeding the apices.
Picture of growth habit.
Close-up picture of narrow panicle inflorescence.
Close-up picture of spikelet.
Close-up picture of hairy lemma.
Close-up picture of subequal glume.
Close-up picture of membranous ligule.
Illustration of Letterman's needlegrass. USDA-NRCS PLANTS Database / Hitchcock, A.S. (rev. A. Chase). 1950. <i>Manual of the grasses of the United States</i>. USDA Miscellaneous Publication No. 200. Washington, DC.