The restoration of plant communities in littoral zones often fails. Because littoral habitats around the world often are subject to changing water regimes and potentially changing future climates, a better understanding of species competitive interactions under such conditions is needed for restoration plant selection. To represent shoreline plant communities, we grew eight freshwater species used in shoreline restoration projects in Minnesota and Wisconsin, USA, in outdoor basins and manipulated water levels to determine the effect on above ground biomass. Biomass production of some species in the competing environment was related to the proximity to water or inundation depth and frequency. Bolboschoenus fluviatilis had biomass differences related to inundation under dry, fluctuating, and normal water manipulations and Schoenoplectus tabernaemontani had biomass differences related to inundation under wet and fluctuating water manipulations, while Carex comosa and Carex lacustris had biomass differences related to placement location under only the wettest water manipulation and Sparganium eurycarpum had biomass differences related to placement location under only the driest water manipulation. Spartina pectinata, Carex vulpinoidea, and Juncus effusus appeared to not have biomass differences related to placement location under any of the water manipulations used. Sparganium eurycarpum and Bolboschoenus fluviatilis dominated the total biomass in all water manipulations. Carex vulpinoidea and Carex lacustris had the least total biomass production in all but one water manipulation. These findings allow for better design of plant community composition and better vegetative erosion control under a variety of water conditions.