Chinese tallow (Sapium sebiferum Roxb.), a naturalized exotic from eastern Asia, forms very dense monotypic stands and has become a serious competitor to native species in stream swamps along the United States Gulf coast. In this experiment, we examined the competitive relationships among seedlings of baldcypress [Taxodium distichum (L.) Rich.], water tupelo (Nyssa aquatica L.), and Chinese tallow in full sun environments under flooded and drained conditions for 2 years. In the drained/mixed stand treatment, leaf biomass of Chinese tallow was 2 and 4 times greater in year 1, and 11 and 27 times greater in year 2 than water tupelo and baldcypress, respectively. Stem biomass was also 1.5 and 10 times greater in year 1 and 8, and 62 times greater in year 2 than water tupelo and baldcypress, respectively. Growth of Chinese tallow under flooded conditions, however, was significantly reduced. Baldcypress and water tupelo both grew better under flooded conditions, with water tupelo growing better than baldcypress. Indications are that Chinese tallow grows faster than native wetland species under moist, well-drained conditions, but flooding significantly reduced growth of the species.