Top of page

« Back to Botany page

Question What is the smallest flower in the world?

Listen to this page

Answer

Watermeal. (Wolffia spp.)

The smallest species of vascular plants in Europe – Spotless watermeal, Wolffia arrhiza – on human fingers.
Every single speck of less than 1 mm length is an individual plant. Christian Fischer, photographer, 2008. Wikimedia Commons

Watermeal (Wolffia spp.) is a member of the duckweed family (Lemnaceae), a family that contains some of the simplest flowering plants. There are various species of the genus Wolffia worldwide, all very small.

Wolffia. Prof. Dr. Thomé’s Flora von Deutschland, Österreich und der Schweiz, in Wort und Bild, für Schule und Haus ; mit … Tafeln … von Walter Müller.
By Otto Wilhelm Thomâe, Gera-Untermhaus: F.E. Köhler, 1889. Biodiversity Heritage Library

The plant itself averages 1/42” long and 1/85” wide or about the size of one candy sprinkle. It can weigh about 1/190,000 of an ounce, equivalent to two grains of table salt. They are very hard to see! Imagine if you tried to fill a thimble with them, it is estimated that you would need some 5000 plants!

Bald cypress swamp and duckweed in Lacassine National Wildlife Refuge. Steve Hillebrand, USFWS photographer. U.S. Fish and Wildlife Service National Digital Library.

Each Wolffia flower consists of a single pistil and stamen; it also produces the world’s smallest fruit, called a utricle. The plant is found in quiet freshwater lakes or marshes with species worldwide. Since the plants have no roots, they can easily float on the surface of the water, where they resemble cornmeal. Watermeal is sometimes used in cold-water aquaria since it is easy to propagate.

An Upper Mississippi River marina covered by excessive duckweed. James Fischer, Wisconsin Department of Natural Resources, photographer. USGS Multimedia Gallery.

Published: 11/19/2019. Updated: 5/2/2024. Author: Science Reference Section, Library of Congress

Related Websites

Plant of the Week- Common duckweed (United States Forest Service)
World’s Smallest Flowering Plant (Wayne's Word at Palomar College) - A page by Wayne Armstrong, a specialist in duckweeds. on Wolffia.
Researchers Study Duckweed’s Potential for Removing Nitrogen (Water Environment Federation: Stormwater Report, June 2014)
The Great Duckweed Migration (Northern Woodlands) - Learn how duckweed sinks and floats in response to seasons.
Miniature Plants with Sizeable Character (University of Florida) - All about duckweed and other tiny plants

Further Reading

Alderton, David. Encyclopedia of aquarium & pond fish. New York, Dorling Kindersley, 2005. 400 p.
Armstrong, Wayne. P. "Duckweeds, California’s smallest wildflowers." Fremontia, v. 10, Oct. 1982: 16-22.
Daubs, Edwin Horace. A monograph of Lemnaceae. Urbana, University of Illinois Press, 1965. 118 p.
Dore, William G. "Wolffia in Canada." Canadian field naturalist, v.71, Jan./Mar. 1957: 10-16.
Giesecke, Ernestine. Pond plants. Chicago, Heinemann Library, c1999. 32 p. (Juvenile literature).
Crow, Garrett E., and C. Barre Hellquist. "Lemnaceae/duckweed family." Aquatic and wetland plants of northeastern North America. Madison, University of Wisconsin Press, c2000. v. 2, p. 78-84.
Saeger, Albert. "Flowering of Lemnaceae." Bulletin of the Torrey Botanical Club, v. 56, Oct. 1929: 351-358.
Skillicorn, Paul, William Spira, and William Journey. Duckweed aquaculture: a new aquatic farming system for developing countries. Washington, World Bank, c1993. 76 p.
Special Issue: "Duckweed ‐ Research and Application." Plant Biology. January 2015: vol. 17, no. s1.

Search Terms

Have a question? Ask a science librarian