This association includes stands with Wolffia arrhiza, a tiny lemnid species, which is usually accompanied by other lemnids. It occurs in alluvial pools, oxbows and channels in broad river floodplains, but it avoids artificial water bodies such as fishponds. Wolffia arrhiza is a thermophilous species occurring rarely in the floodplains of the lower Dyje and Morava rivers in southern Moravia.