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Montana Field Guide

Montana Field Guides

Common Hornwort - Ceratophyllum demersum
Other Names:  Rigid Coontail

Native Species

Global Rank: G5
State Rank: S5

Agency Status
MNPS Threat Rank:
C-value: 4

External Links

General Description
Aquatic, perennial, monoecious herbs without roots. Stems flaccid, floating, up to 3 m. Leaves 3 to 11 per node, 7–30 mm long, forked into few linear, apiculate-toothed segments. Flowers unisexual, solitary in leaf axils; petals and sepals absent; involucre of 8 to 15 simple or forked, linear segments; stamens 3 to 50; pistil solitary. Fruit a 1-seeded achene, 4–6 mm long, narrowly elliptic and compressed with 1 terminal and two basal spines, shorter to much longer than the body (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Species Range
Montana Range


Range Comments
Cosmopolitan, absent from the northernmost parts of North America (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 2047

(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 to deep, fresh or brackish water of lakes, ponds, slow streams; plains, valleys (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Craig, V.E. 1952. A story of fish production as it applies to Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 92 p.
    • Garrett, P.A. 1983. Relationships between benthic communities, land use, chemical dynamics, and trophic state in Georgetown Lake. Ph.D. Dissertation. Bozeman, MT: Montana State University. 136 p.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
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Citation for data on this website:
Common Hornwort — Ceratophyllum demersum.  Montana Field Guide.  .  Retrieved on , from