Duckweeds are the smallest of the flowering plants, which consist of tiny, green, rounded, leaflike bodies (fronds) that float on the water’s surface. Several duckweed plants can fit easily on a fingertip. They occur singly or connected in groups. They usually reproduce by budding, but do (rarely) produce tiny, simple, male and female flowers. Missouri has 8 species of duckweeds (genus Lemna), 2 of giant duckweed (Spirodella), and 3 of watermeal (Wolffia).
Each duckweed plant (genus Lemna) is a green, leaflike circular or oval frond less than 1/4 inch across, each bearing a single short, hairlike root that dangles into the water.
Giant duckweeds grow in clusters of 1-3, with 2-20 roots per frond. Each frond can be nearly 3/8 inch across.
The watermeal genus includes the smallest flowering plants known; each plant is about the size of a pinhead and lacks roots; they look like tiny green dots.