Duckweeds are tiny flowering plants that float on ponds and other still fresh water. Each plant is a small, leaf-like body called a frond, and some kinds have roots hanging below. The explorer shows one frond 2 millimeters (0.08 inches) long, within the range of common duckweed, Lemna minor, whose fronds are 1–8 millimeters long.

Size

A duckweed has no true stem. Its frond is only a few cells thick, and air spaces inside it keep it afloat. Across all the duckweeds, fronds range from 1 to 15 millimeters in length or width.

Common duckweed has egg-shaped fronds 1–8 millimeters long and 0.5–6.2 millimeters wide. Its single root can grow up to 15 centimeters (6 inches) long. The explorer's 2-millimeter frond sits toward the small end of the species' range.

Size comparisons

• About 13 fronds 2 millimeters long, laid end to end, would span one inch (2.54 centimeters).
• A 2-millimeter frond is nearly three times as long as a 0.7-millimeter mechanical pencil lead is wide.
• Four grains of table salt 0.5 millimeters across would fit along its length.
• A root 15 centimeters long is 75 times the length of a 2-millimeter frond.
• Columbian water-meal, one of the smallest flowering plants, is 0.5–1.4 millimeters long, so a 2-millimeter frond is 1.4–4 times its length.

How duckweed grows

Duckweeds can flower and make seeds, but they grow mainly by budding: new daughter fronds grow out of one or two pouches in the mother frond. The fronds stay joined for a while, forming small colonies that spread across the water.

As of 2025, duckweeds are the fastest-growing flowering plants known. A 2018 study listed a doubling time of about one day for Wolffia microscopica, the fastest-growing species. Under good conditions, duckweed can cover a pond within a few days. Because the plants take up nutrients and pollutants from the water as they grow, they can also be used to clean polluted water.

The smallest flowering plants

The smallest duckweeds belong to the genus Wolffia, called water-meal. Columbian water-meal, Wolffia columbiana, has no roots. As of 2026, the botanical guide Go Botany describes it as generally considered the smallest flowering plant on Earth.

In Thailand, another species, Wolffia globosa, is sold in vegetable markets under local names meaning "water eggs". It is eaten in salads, omelets and curries. Water-meal plants are 20–30% protein by dry weight.

Sources

• Lemna minor: Common Duckweed. Go Botany, Native Plant Trust.
• Wolffia columbiana: Columbian Water-meal. Go Botany, Native Plant Trust.
• Developments in Toxicity Testing with Duckweeds. Paul Ziegler, Journal of Xenobiotics, 2025.
• Nutritional Value of the Duckweed Species of the Genus Wolffia (Lemnaceae) as Human Food. Appenroth et al., Frontiers in Chemistry, 2018.
• ISO 20318-2:2019, Mechanical Pencils and Leads for General Use, Part 2: Black Leads (preview). International Organization for Standardization, 2019.
• Salt, the Only Rock We Eat!. Henry Shaw, UC Master Food Preserver Program, University of California Agriculture and Natural Resources, 2025.