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Montana Field Guide

Montana Field Guides

Lesser Duckweed - Lemna minor
Other Names:  Common Duckweed, Water Lentil

Native Species

Global Rank: G5
State Rank: S5

Agency Status
MNPS Threat Rank:
C-value: 6

External Links

General Description
Frond ovate, 1–8 mm long; solitary or in small clusters, often purplish on the lower surface. Roots 1–15 mm long (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Diagnostic Characteristics
Montana species of the Duckweed Family are all small, perennial, free-floating, aquatic herbs distinguished by their veins and roots. Veins are best observed using a 10x magnification and back-lighting (Giblin et al. [eds.] 2018) or by placing on a transparent slide (Landolt in FNA 2000). Landolt in FNA (2000) provides some techniques to analyze anatomy. In this family the term "leaf" cannot be used because a leaf consists of a stem (petiole) and a blade (Landolt in FNA 2000). Instead the term "frond" is used. Be aware that species can grow in the same place naturally.

Lemna - Duckweed, native
* Fronds: Green above and mostly below.
* Root: 1 per frond, sometimes absent.
* Veins: 1-3 per frond.

Spirodela - Duck-meal, native
* Fronds: Green above and usually purplish below.
* Roots: 2 or more per frond
* Veins: 3 or more per frond.

Wolffia - Water-meal, native
* Fronds: Green to brown.
* Root: 0; absent.
* Veins: 0; absent.

Lesser Duckweed - Lemna minor, native
*Compare to Lemna turionifera.
*Fronds: at least some are more than 2 mm long, roundish, green on top and often purplish on bottom.
*Turions: Absent.
*Fruit: 0.8-1 mm long. Seeds with 8-15 distinct ribs.
*Habitat: Permanent, slow moving water of ponds, lakes, and streams.

Turion Duckweed - Lemna turionifera, native
*Compare to Lemna minor.
*Fronds: 1-4 mm long, nearly oval, flat, green on top and bottom, sometimes red to purplish on bottom. Red to purple color emanating from the root.
*Turions: Produced under stress. Olive, brown, or dark green rootless disk-like, 0.8-1.6 mm wide, that sink.
*Fruit: 0.5-0.6 mm long. Seeds with 30-60 distinct ribs.
*Habitat: Calm waters.

Pale Duckweed - Lemna valdiviana, native, SOC
*Fronds: 1-2 mm long, oblong, green on top and bottom.
*Turions: Absent.
*Habitat: Warm Springs; possibly also lakes and rivers.

Inflated Duckweed - Lemna gibba, native
*Fronds: Less than 6 mm long, nearly oval, greenish on top and bottom or red to purplish on bottom. Red to purple color emanating from the margins.Inflated which can be seen in cross-section, making their lower surface convex.
*Turions: Absent.
*Habitat: Calm waters of ponds and lakes.

Star Duckweed - Lemna triscula, native
*Fronds: 6-12 mm long, oblong to lanceolate and attached together by elongated stipes to appear like a 'canoe paddle', and greenish on top and bottom.
*Turions: Absent.
*Veins: 3 and faint.
*Habitat: Fresh to somewhat alkaline water of ponds, lakes, and marshes.

Species Range
Montana Range


Range Comments
Circumboreal south to most of temperate North America (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 126

(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)

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

Duckweed plants that grow in shaded habitats may be twice the size of those growing in full sun (Giblin et al. [eds.] 2018). Members of the Duckweed Family have a high productivity rate with particular species able to double their population with a 24-hour window (Landolt in FNA 2000). Species of the Duckweed Family tend to be very rare in places with high or very low precipitation (Landolt in FNA 2000).

Plants in the Duckweed Family are easily transplanted over short distances by birds (Landolt in FNA 2000). Duckweed species have a high nutritive value with up to 45% of their dry weight consisting of amino acids, the building blocks for protein (Landolt in FNA 2000; Culver and Lemly 2013). They provide food for fish, snapping turtles, and waterfowl and create habitat for aquatic invertebrates (Culver and Lemly 2013). Certain species are cultivated as feed for poultry, pegs, and cows (Landolt in FNA 2000).

Species of the Duckweed Family are used for waste-water purification and as test- and indicator- plants for detecting certain conditions (Landolt in FNA 2000).

  • Literature Cited AboveLegend:   View Online Publication
    • Culver, D. and J. Lemly. 2013. Field Guide to Colorado's Wetland Plants: Identification, Ecology and Conservation. Fort Collins, CO: Colorado Natural Heritage Program. 694 p.
    • Flora of North America Editorial Committee (FNA). 2000. Flora of North America north of Mexico. Vol. 22. Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford Univ. Press, New York. xxiii + 352 pp.
    • Giblin, David E., Ben S. Legler, Peter F. Zika, and Richard G. Olmstead (editors). 2018. Flora of the Pacific Northwest: An Illustrated Manual. Second Edition. University of Washington Press in Association with Burke Museum of Natural History and Culture, Seattle, Washington. 882 pp.
    • 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?
    • Cope, M.G. 1992. Distribution, habitat selection and survival of transplanted Columbian Sharp-tailed Grouse (Tympanuchus phasianellus columbianus) in the Tobacco Valley, Montana. M.Sc. Thesis. Bozeman, Montana: Montana State University. 60 p.
    • Craig, V.E. 1952. A story of fish production as it applies to Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 92 p.
    • Dorn, R. D. 1984. Vascular Plants of Montana. Cheyenne, WY: Mountain West Publishing. 276 pp.
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Citation for data on this website:
Lesser Duckweed — Lemna minor.  Montana Field Guide.  .  Retrieved on , from