Individuals of giant duckweed are called fronds. Each frond consists of a small, green, floating body (less than 10 mm) with a several roots (7-21) that extend into the water from the undersurface, but the roots do not normally reach the soil. The undersurface of giant duckweed is usually red.

Giant duckweed plants rarely flower. Instead, they reproduce by simple division of a frond to produce a new "daughter" frond. Duckweeds in general do best in full sun and in nutrient rich water. Under those conditions they can grow rapidly, by repeated division of the fronds. The developing daughter fronds remain attached to the "mother" frond long enough to commonly give the appearance of a several-lobed structure, as shown at far right above.

A good source of information on giant duckweed and related plantscan be found in the book: Flora of North America Editorial Committee, eds. 2000. Flora of North America North of Mexico. Vol. 22. Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford University Press. pp143-153. This publication is also available on line and the portion dealing with Spirodela polyrhiza can be found at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200027353