A major topic of discussion in community ecology is the relative influence of proximate seed sources and environmental variability on local plant species diversity. We investigated the effect of adjacent seed sources and environmental factors on initial plant species richness and composition in sixty wetland basins created in central Kansas, USA in 1998. We defined the adjacent seed source for each basin as the list of plant species found within a 10-m radius around each basin, filtered for those species capable of growing in wetland conditions. Basin water levels were monitored biweekly over three growing seasons, starting in 1999, as were soil moisture, temperature, and conductivity. Soil samples were analyzed for total nitrogen, total phosphorus, pH, and soluble salts in 2001. We found that in the three-year-old basins, the species richness of the adjacent areas had contributed significantly to basin species richness, as did basin area, soil pH, and water-level fluctuation. After three years, 61% of the species found in the adjacent areas were also found in the basins. While we found that proximate seed sources did influence initial species richness and composition in newly created wetlands, we cannot conclude that any differences in initial plant communities will ultimately result in different successional trajectories for the wetlands in our system. However, given the potential sensitivity of vegetation richness and composition in these newly created wetlands to proximate seed sources, the location of future wetland creations may need to be considered.