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Duckweed

Duckweed is a common name for very small, free-floating aquatic flowering plants in the duckweed family (Lemnaceae), now usually treated within the arum family, Araceae.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 27, 2026|2 min read| Fact-checked

Duckweed is a common name for very small, free-floating aquatic flowering plants in the duckweed family (Lemnaceae), now usually treated within the arum family, Araceae. These plants form green mats on still or slow-moving freshwater and reproduce rapidly, mainly by budding or division. Some species are among the smallest flowering plants known.

Description

Duckweeds are minute aquatic plants with simple, leaf-like floating bodies called fronds. Some species have one or more slender roots, and flowering is uncommon.

Taxonomy

Duckweed is a common name for several genera, including Lemna, Spirodela, Landoltia, Wolffiella, and Wolffia. Modern classifications often place them in the arum family, Araceae.

Ecology and habitat

They grow in ponds, lakes, wetlands, canals, and other still or slowly moving waters, especially where nutrients are abundant. Dense growth can shade submerged plants and reduce oxygen levels, but the plants also support aquatic wildlife.

Uses and research

Duckweeds are being studied as a source of protein, biomass, and for phytoremediation and wastewater treatment. Their rapid growth and simple structure make them useful in applied research.

Key facts

  • Duckweed is not one species, but a common name for several tiny aquatic plant species.
  • Plants float on the water surface and often form dense green mats.
  • They reproduce rapidly, usually by budding or division rather than by flowers or seeds.
  • Duckweeds are among the smallest flowering plants known.
  • They can provide food and shelter for aquatic wildlife, but can also become invasive in nutrient-rich water.
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Canadian context

Duckweed is relevant in Canada because it occurs in freshwater habitats and is of interest for pond ecology, nutrient pollution, and water treatment research. Canadian readers may encounter it in wetlands, ponds, and managed waterways, where it can be either beneficial wildlife cover or an overgrowth problem.

Frequently asked questions

What is duckweed?
Duckweed is a collective name for tiny free-floating aquatic flowering plants that usually form green mats on the surface of still freshwater.
Is duckweed a single species?
No. It refers to several related species across multiple genera, including Lemna, Spirodela, Landoltia, Wolffiella, and Wolffia.
How does duckweed reproduce?
It usually reproduces vegetatively, by budding or division. Flowers and seeds occur, but only rarely.
Where does duckweed grow?
Duckweed grows in still or slow-moving freshwater such as ponds, lakes, canals, and wetlands, especially in warm, nutrient-rich water.
Why is duckweed sometimes considered a weed?
It can spread quickly and cover water surfaces, which may shade other plants and lower oxygen levels in the water.
What is duckweed used for?
Duckweed is studied for animal feed, human food, biomass, wastewater treatment, and removing pollutants from water.

References

  1. Missouri Department of Conservation — https://www.mdc.mo.gov/discover-nature/field-guide/duckweeds-watermeal
    Supports: Duckweeds are the smallest flowering plants, float on water, reproduce mainly by budding, and occur in multiple species/genera.
  2. USDA Forest Service — https://www.fs.usda.gov/wildflowers/plant-of-the-week/lemna_minor.shtml
    Supports: Duckweeds are among the smallest flowering plants known.
  3. Royal Horticultural Society — https://www.rhs.org.uk/weeds/duckweed
    Supports: Duckweeds are free-floating aquatic perennials, form surface carpets, and can be beneficial or problematic in ponds.
  4. USDA — https://www.usda.gov/sites/default/files/documents/Duckweed_Factsheet.pdf
    Supports: Duckweed is among the smallest, fastest-growing plants and is studied for bioenergy and protein.
  5. PubMed Central — https://pmc.ncbi.nlm.nih.gov/articles/PMC8525856/
    Supports: Duckweeds are floating plants, occur worldwide except polar regions, and are studied for food, phytoremediation, and industrial applications.
  6. Wikipedia — https://en.wikipedia.org/wiki/Lemnoideae
    Supports: Duckweed genera include Spirodela, Landoltia, Lemna, Wolffiella, and Wolffia.