Lemna trisulca (Star Duckweed)

Plant Info
Also known as: Ivy-leaved Duckweed, Forked Duckweed
Family:Araceae (Arum)
Life cycle:perennial
Habitat:sun; quiet water to 4+ feet deep; lakes, ponds, creeks, rivers, ditches
Bloom season:June - July
Plant height:less than 1 mm
Wetland Indicator Status:GP: OBL MW: OBL NCNE: OBL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct

Plants rarely flower, but will float on the water's surface when they do. Flowers are contained in a lateral pouch, lack petals or sepals and have 2 stamens and a single style.

Leaves and stems: Leaf attachment: alternate Leaf attachment: opposite Leaf attachment: whorl Leaf type: simple

[photo of leaves and stem] Leaves, known as fronds, are 3 to 15 mm (to ½+ inch) long, 2 to 3.5 times as long as wide, narrowly egg-shaped to oblong-elliptic, blunt to rounded at the tip, often with a few minute teeth at the tip end (magnification required), and tapering at the base to a flat stem. Color is usually green, sometimes purplish. A frond may have a single, thread-like root up to about 1 inch long, though roots may be absent altogether.

[photo of branched chains] Branched chains are formed with offshoots from a frond, which then offshoots another one or two stems and fronds and so on, a single chain having up to 50 fronds. Vegetative plants float just below the water's surface, not on the surface, and often form dense, tangled masses with thousands of chains.

Fruit: Fruit type: seed without plume

Like the rare flower, fruit—a tiny seed less than 1 mm long—is rarely produced.


Star Duckweed is very common in Minnesota and not likely to be mistaken for any other species; the leaf shape and branching chains are quite distinctive. It may be overlooked since it is rarely seen floating but there is no mistaking it once you get a closer look. Like other Duckweeds, it's found in the quiet waters of lakes, ponds and slow-moving streams.

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More photos

Photos by K. Chayka taken in Anoka County.


Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: gary - Carlton County
on: 2022-10-01 10:05:13

A few plants mixed with various larger aquatic plants in an old beaver pond.

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