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Montana Field Guide

Montana Field Guides

Coville's Rush - Juncus covillei

Species of Concern
Native Species

Global Rank: G5
State Rank: S2S3
* (see State Rank Reason below)

Agency Status
MNPS Threat Rank:
C-value: 4

External Links

State Rank Reason (see State Rank above)
Rare and peripheral in Montana. Currently known from approximately a half-dozen widely scattered wetland/riparian sites in the mountainous portion of the state.
  • Details on Status Ranking and Review
    Coville's Rush (Juncus covillei) Conservation Status Review
    Review Date =
General Description
Rhizomatous. Stems erect, compressed, 6–20 cm, sometimes clumped. Leaves basal and cauline; blades flat, 1–2 mm wide; auricles acute or absent. Inflorescence congested with 3 to 7 sessile flowers in each of 1 to 3 clusters; main bract shorter or longer than the inflorescence. Flowers: prophylls absent; tepals brown to purplish with a green midstripe, 3–4 mm long, acute; stamens 6. Capsules 3–5 mm long, truncate on top; seeds without appendages (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

We have varieties covillei and obtusatus C.L. Hitchc.

Fruits reach maturity from late August-September

Diagnostic Characteristics
Juncus is a large and difficult genus to distinguish, so a technical key should be consulted. Mature fruit is necessary for positive determination. The combination of flowers subtended by a single bract, flattened leaves, and 7-flowered heads separate J. covillei from most other rhizomatous rushes. The tepals of var obtusatus are pale brown, and the inner ones have pointed tips. In contrast, the tepals of variety covillei are dark brown, and the inner tepals have rounded tips.

Species Range

Range Comments
BC to CA, ID and MT (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

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)

Variety covillei is typically found in moist, gravelly or sandy soil along major water courses in the valley zone. In contrast, variety obtusatus is found in moist to wet, often seepy soil of slopes and meadows in the montane and subalpine zones.

Ecological Systems Associated with this Species

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Citation for data on this website:
Coville's Rush — Juncus covillei.  Montana Field Guide.  .  Retrieved on , from