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Montana Field Guide

Montana Field Guides

Western Sedge - Carex occidentalis

Species of Concern
Native Species

Global Rank: G4
State Rank: SH
(see State Rank Reason below)

Agency Status
MNPS Threat Rank:

External Links

State Rank Reason (see State Rank above)
Known in Montana from an 1887 collection by Tweedy near "Boulder Creek" and a 1930 collection on Willow Creek in Beaverhead County.
General Description
Western Sedge has short, creeping rootstocks and forms loose bunches with flowering stems that are sharply triangular and up to 80 cm tall. The leaves are flat with inrolled margins and 103 mm wide. The inflorescence consists of 4-10 spikes, tightly clustered towards the top but more remote at the bottom; each spike is oblong and 15-30 mm long with inconspicuous male flowers at the top. The green to straw-colored perigynia point upward in the spike; they are oblong-elliptic, 2-5 mm long, and mostly concealed by the brownish, ovate-triangular scales that have a white margin and a green center. The lens-shaped achene nearly fills the body of the perigynium.

Flowering and fruiting in June-July.

Diagnostic Characteristics
Carex is a large genus, making individual species identification difficult at times. The bunch-forming growth form, elongate heads and elliptic perigynia are among the more diagnostic characteristics of this species among upland Carex. Mature fruit and a technical key are essential in order to separate this from closely related species.

Species Range

Range Comments
MT (where evidently extirpated from the southwest) east to SD, south to CA and TX; most common in CO, UT AZ and NM (Kartesz in prep. 2012).

Observations in Montana Natural Heritage Program Database
Number of Observations: 9

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Dry habitats in montane zone, extending to spruce-fir habitat and sometimes to subalpine or alpine zones.

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Citation for data on this website:
Western Sedge — Carex occidentalis.  Montana Field Guide.  .  Retrieved on , from