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Carex occidentalis Bailey

Western sedge

Cyperaceae (Sedge family)

General Description: A grass-like perennial forming loose bunches of sharply triangular stems up to about 80 cm tall. Leaves are flat, 1-3 mm wide, elongate, but shorter than the stems, and not all clustered at the very base of the plant. The inflorescence is a more or less slender, cylindric head comprised of 4-10 aggregated spikes more tightly clustered toward the top of the inflorescence than at the bottom. Spikes are small, few-flowered, and have male flowers above the female. The perigynia have 2 stigmas, are finely serrulate above the middle, 3-5 mm long, greenish-straw to coppery brown in color, and with sharp, narrow, green, shiny margins. Scales are brownish with a whitish margin, ovate-triangular, pointy-tipped, and largely conceal the perigynia.

Illustration.

Field Identification Tips: Western sedge occurs in relatively dry habitats. Field characteristics include its tufted habit, elongated, greenish-straw-colored inflorescence, heads having male flowers above the female, and shiny perigynia with narrow, often green margins. Positive identification requires use of a technical key and hand lens or microscope.

Phenology: July and August.

Similar Species: Many other sedge species resemble western sedge in general appearance. It is most likely to be confused with other tufted sedges that can occur in upland habitats, and have male flowers above the female in the inflorescences. Carex hoodii (Hood's sedge) has spikes that are more tightly clustered and more markedly bicolored. Carex vallicola (valley sedge) does not get over about 40 cm tall, and has pale scales usually shorter than the perigynia. Carex tumulicola (foothill sedge) usually has bracts subtending and surpassing the lower spikes of the inflorescence.

Habitat: Dry, open, or lightly wooded slopes, less often in meadows, generally at middle, but extending upward to subalpine and alpine areas. The Idaho collection was made in a lava field.

Global Distribution: Wyoming to New Mexico, Arizona, Utah, Nevada, and southern California. Historical collections of western sedge are known from southwestern Montana and eastern Idaho. The southern Rocky Mountain Range forms the core of this species' distribution.

Idaho Distribution: Known from a historical collection about 10 miles southwest of Idaho Falls in Bonneville County.

References:

Hurd, E., N. L. Shaw, J. Mastrogiuseppe, L. Smithman, and S. Goodrich. 1998. Field guide to Intermountain sedges. General Technical Report RMRS-GTR-10. U.S. Forest Service, Rocky Mountain Research Station, Ogden, UT. 282 pp.

Montana Natural Heritage Program. Montana rare plant field guide. Available at: http://nhp.nris.state.mt.us.