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Montana Field Guide

Montana Field Guides

Whorled Water-milfoil - Myriophyllum verticillatum

Status Under Review
Undetermined Origin

Global Rank: G5
State Rank: SU

Agency Status
MNPS Threat Rank:
C-value: 4

External Links

General Description
Stems whitish, branched. Leaves 4-whorled, to 45 mm long, divided into 18 to 34 filiform segments. Bracts 3–8 mm long; longer than the fruits pectinate, 1 to 2 times as long as flowers. Female flowers with sepals <1 mm long; petals absent; bracts minute. Male flowers with small, yellowish petals; bracts dentate; stamens 8. Mericarps 2–3 mm long (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)..

Species Range

Range Comments
AK to NL south to CA, AZ, TX, IL, WV; Europe. Collected in Flathead, Lincoln, and Sweet Grass counties; reported for Sanders and several other counties (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 25

(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 rather deep water of ponds, lakes; plains, valleys to montane (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

  • Additional ReferencesLegend:   View Online Publication
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    • Aiken, S.G. 1981. A Conspectus of Myriophyllum (Haloragaceae) in North America. Brittonia 33 (1): 57-69. A81AIK01PAUS.
    • Britton, N. L. and A. B. Brown. 1913. An Illustrated Flora of the Northern United States, Canada, and the British Possessions. 2nd Edition in 3 Volumes. New York, NY: Charles Scribner's Sons. B13BRI01PAUS.
    • Fassett, Norman C. 1940. A Manual of Aquatic Plants, 1st ed. New York: McGraw-Hill. B57FAS01PAUS.
    • Fernald, M. L. 1950. Gray's manual of botany. Eighth edition. A handbook of the flowering plants and ferns of the central and northeastern United States and Adjacent Canada. American Book Co., New York.
    • Gleason, H. A., and A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. New York Botanical Garden, Bronx, NY. 910 pp.
    • Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Linnaeus, C. 1753. Species Plantarum. A fascimile of the first edition printed by Adlard & Son, Bartholomew Press, Dorking, Great Britain. 2 vol.
    • Weishaupt, C.G. 1971. Vascular Plants of Ohio, Third Ed. Kendall/Hunt Publishing Co. Dubuque, Iowa. B71WEI01PAUS
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Citation for data on this website:
Whorled Water-milfoil — Myriophyllum verticillatum.  Montana Field Guide.  .  Retrieved on , from