During two growing seasons, the monthly biomass was determined for the dominant plants at three tidal marshes within the lower Pearl River basin, Louisiana. There were differences between the two growing seasons in ecological dominance and production. Ten species (<em>Spartina patens</em>, <em>Sagittaia lancifolia</em>, <em>Phyla nodiflora</em>, <em>Peltandra virginica</em>, <em>Vigna luteola</em>, <em>Saururus cernuus</em>, <em>Polygonum sagittatum</em>, <em>Panicum gymnocarpon</em>, and <em>Eleocharis</em> spp.) accounted for 98% of the marsh productivity. Using the Smalley method, net aboveground primary production was 1241 g/m2/yr for the freshwater marsh, 1745 g/m2/yr for the intermediate salinity marsh, and 2259 g/m2/yr for the brackish marsh. The peak total biomass for the freshwater marsh was 1205 g/m2, for the intermediate marsh it was 1103 g/m2, and for the brackish marsh it was 3089 g/m2. By summing the annual live standing biomass for each species, primary production estimates for each marsh site were lower than those calculated by the Smalley method: 1190 g/m2/yr for the freshwater marsh, 964 g/m2/yr for the intermediate marsh, and 1121 g/m2/yr for the brackish marsh.