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Montana Field Guide

Montana Field Guides

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

Species of Concern

Global Rank: G4G5
State Rank: S2?
* (see State Rank Reason below)

Agency Status
MNPS Threat Rank: 3
C-value: 8

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 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

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

Summary of Observations Submitted for Montana
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)

Shallow water of ponds and lakes on the plains.

Ecological Systems Associated with this Species

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Citation for data on this website:
Long-sheath Waterweed — Elodea bifoliata.  Montana Field Guide.  .  Retrieved on , from