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Montana Field Guide

Montana Field Guides

Western Quillwort - Isoetes occidentalis
Other Names:  Isoetes lacustris var. paupercula

Species of Concern
Native Species

Global Rank: G4G5
State Rank: S1
(see State Rank Reason below)

Agency Status
MNPS Threat Rank:
C-value: 9

External Links

State Rank Reason (see State Rank above)
Isoetes occidentalis is known from two locations in northwest Montana. Survey work to identify other locations, document population sizes, and determine threats is greatly needed.
General Description
Plants aquatic. Leaves to 20 cm, gradually tapering. Sporangia 3–6 mm long. Megaspores 0.4–0.8 mm wide (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Range Comments
Alaska, British Columbia, and California, east to Montana, Wyoming and Colorado.

Observations in Montana Natural Heritage Program Database
Number of Observations: 4

(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)

Our one record is from shallow water of a montane lake in Missoula County (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

  • 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?
    • Pierce, John. 1998. Montana specimen of Isoetes occidentalis. Collection number 2136. Deposited at University of Montana Herbarium (MONTU). Missoula, Montana. Accessible at the Consortium of Pacific Northwest Herbaria.
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Citation for data on this website:
Western Quillwort — Isoetes occidentalis.  Montana Field Guide.  .  Retrieved on , from