Photo © Robert K. Moseley CLICK PHOTO FOR A LARGER IMAGE

Piptatherum micranthum (Trin. & Rupr.) Barkworth

Small-flowered ricegrass

Poaceae (Grass family)

Synonym: Oryzopsis micrantha (Trin. & Rupr.) Thurb.

General Description: A strongly tufted perennial grass 30-70 cm tall. Leaf blades are flat or slightly inrolled, 1-2 mm wide, while sheaths are open and smooth to slightly pubescent with fine, short hairs. Ligules are small, up to about 1 mm long and finely hairy along the edges. The inflorescence is a narrow panicle 7-15 cm long having short, ascending or slightly spreading branches. Glumes are equal, papery, transparent, sharply pointed, and about 3-4 mm long. Lemmas are hairless or occasionally have fine hairs and have a straight, stiff awn 4-8 mm long. They are also shiny and become hard and brownish in color. The callus is also hairless. Anthers are about 1 mm long.

Illustration.

Field Identification Tips: Small-flowered ricegrass is recognized by its tufted habit, thin leaves, narrow panicle with ascending or slightly spreading branches, glabrous callus, and lemmas becoming shiny, brownish, and hardened as they mature and having a straight, relatively long awn.

Phenology: Flowers June to early August.

Similar Species: Small-flowered ricegrass could to be confused with Piptatherum exiguum (Oryzopsis exigua). This species differs in its spike-like, appressed inflorescence and obviously bent awn of the lemma. Some species of Achnatherum (Stipa in part) can also look similar, but differ in having lemmas with longer (usually >15 mm), often bent, and sometimes pubescent awns, and a hairy callus.

Photo © Robert K. Moseley CLICK PHOTO FOR A LARGER IMAGE

Habitat: Dry, open, often sandy soil or rocky ridge areas from the sagebrush foothills to open forests at middle elevations. The known Idaho population occurs in cracks and on ledges in a limestone cliff alcove. It has no associates at this site.

Global Distribution: British Columbia to Saskatchewan, south to eastern California and Texas.

Idaho Distribution: Known from the Birch Creek Valley south of Blue Dome in Clark County.

References:

Cronquist, A., A. H. Holmgren, N. L. Holmgren, J. Reveal, and P. K. Holmgren. 1977. Intermountain Flora. Vascular plants of the Intermountain West, U.S.A. Vol. 6. Published for The New York Botanical Garden by Columbia University Press, NY. 584 pp.

Stewart, H., and R. Hebda. Grasses of the Columbia Basin of British Columbia. Available at http://livinglandscapes.bc.ca/cbasin/cb_grasses/index-grasses.html.