Duckweeds are the smallest flowering and fastest growing aquatic plants known, they have a high biomass production rate, as they can double their biomass in 96 hours which makes them an excellent feedstock for environmentally sustainable and economically viable production of biofuels and protein. In this research, growth of three duckweed species, Lemna gibba L., L. minor L. and Spirodela polyrhiza L. Schleiden was studied in 7 days-long laboratory tests at the department of Botany, University of Debrecen, to evaluate the growth of the cultures, along with the various co- culturing arrangements of species. Growth in different combinations of species was recorded by digital photographs and calculated based on the summarized frond area of the cultures by relative growth rate while the species-level growth was determined by visual inspection.