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Montana Field Guide

Montana Field Guides

Long-sheath Waterweed - Elodea bifoliata
Other Names:  Elodea longivaginata

Species of Concern
Native Species

Global Rank: G4G5
State Rank: S2?
(see State Rank Reason below)
State Threat Score: No Known Threats
C-value: 8

Agency Status


External Links

State Rank Reason (see State Rank above)
Rare in Montana, where it is currently known from a few widely scattered locations across the state. Additional population and trend data are needed for the species within Montana.
General Description
Leaves opposite, 10–20 × 1.5–2.5 mm, minutely serrate, narrowly lanceolate to linear. Male flowers: spathe 2–5 cm long, inflated above; sepals 3–5 mm long; petals 4–5 mm long; stamens 7 to 9. Female flowers: spathe 3–7 cm long, slightly inflated above; sepals 2–3 mm long; petals 3–4 mm long. Capsule 8–10 mm long (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Flowering in late June-July.

Diagnostic Characteristics
Elodea can be distinguished from other aquatic plants by the long-stalked, floating flowers. Elodea bifoliata can be distinguished from other members of the genus by its opposite rather than whorled leaves.

Species Range
Montana Range Range Descriptions


Range Comments
BC to MN south to OR, UT and NM (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 85

(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)

Shallow water of ponds and lakes 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

Threats or Limiting Factors
Threat impact not assigned because threats are not known (MTNHP Threat Assessment 2021).

  • 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?
    • Catling, P.M., and W. Wojtas. 1986. The waterweeds (Elodea and Egeria, hydrocharitaceae) in Canada. Can. J. Bot. 64:1525-1541.
    • 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.
  • Web Search Engines for Articles on "Long-sheath Waterweed"
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Citation for data on this website:
Long-sheath Waterweed — Elodea bifoliata.  Montana Field Guide.  .  Retrieved on , from