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Montana Field Guide

Montana Field Guides

Tapered Rush - Juncus acuminatus

Species of Concern
Native Species

Global Rank: G5
State Rank: S1
(see State Rank Reason below)
State Threat Score: Unknown
C-value: 5

Agency Status


External Links

State Rank Reason (see State Rank above)
Rare in Montana. Only known in the state from one wetland site in Teton County.
General Description
Short-rhizomatous, caespitose. Stems erect, terete, 40–80 cm, tufted. Leaves basal and cauline; blades subterete, 1–2 mm wide; auricles rounded. Inflorescence open with erect branches and clusters of 10 to 20+ flowers ca. 1 cm across; main bract shorter than the inflorescence. Flowers: prophylls absent; tepals green to light brown, 2–4 mm long, acuminate; stamens 3. Capsules 2–4 mm long, slightly exserted, tapering to the beak; seeds apiculate (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Mature fruit in late July.

Diagnostic Characteristics
The septate leaves and flowers subtended by a single bract and having only 3 stamens separate J. acuminatus from our other non-rhizomatous rushes. Juncus is a large and difficult genus to distinguish, so a technical key should be consulted. Mature fruit is necessary for positive determination.

Species Range
Montana Range Range Descriptions


Range Comments
BC to NS south to most of U.S., Mexico, S. America, rare on the Great Plains. One collection from Teton County (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 3

(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)

Wet soil on the margins of ponds and marshes in the valley zone and on the plains.
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

Ecological Systems Associated with this Species
  • Commonly Associated with these Ecological Systems
    Wetland and Riparian Systems

  • Literature Cited AboveLegend:   View Online Publication
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Hermann, F.J. 1975. Manual of the rushes (Juncus spp.) of the Rocky Mountains and Colorado basin. U.S. Forest Service, General Technical Report RM-18.
    • Lesica, P. 1991. The Rare Vascular Plants of Pine Butte Swamp Preserve. Unpublished Report to the Nature Conservancy. 15 Pp.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
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Citation for data on this website:
Tapered Rush — Juncus acuminatus.  Montana Field Guide.  .  Retrieved on , from