Duckweeds grow as free-floating thalli on or just beneath the water surface. Most are small, not exceeding 5 mm in length, except Lemna trisulca which is elongated and has a branched structure.
Lemna thalli have a single root, which distinguishes them from related genera Spirodela.
Examples on this collage are in the upper row left to right Common Duckweed (Lemna minor_), Gibbous Duckweed (Lemna gibba_), bottom left Ivy Duckweed (Lemna trisulca), bottom right Giant Duckweed (Spirodela polyrhiza).
Duckweeds grow mainly by vegetative reproduction, which allows very rapid colonization of water surfaces reducing undesirably the aeration of water layers beneath thick duckweed mats. On the other hand they may help in bio-remediation of polluted waters via quickly utilizing excessive amounts of plant nutrients. They excrete proteins of pharmaceutical interest consequently are useful and important testing and producing organisms in pharmaceutical research and in producing pharmaceuticals.
Carefully managed duckweed farms can produce 10 to 30 tons of valuable dried duckweed per hectare per year.
The background photo of the composite taken at the Utah Lake is courtesy of Linda Fortner, The Orchid Lady.