Aeschynomene virginica is a freshwater, tidal plant ranging from southern New Jersey to central North Carolina. This plant is listed as threatened in the United States. Population sizes vary greatly from year to year and population sites are often unoccupied several years before re-establishment. Despite long-term population monitoring and experiments, it is not clear if seed banks and seed dispersal or only seed banks re-establish unoccupied population sites. The removal of a dam on Vandell Preserve, New Kent County, Virginia, created a natural experiment that helps clarify the role of seed bank and seed dispersal processes. The establishment of new A. virginica populations on long-covered soils devoid of a seed bank would indicate successful seed dispersal. I review the seed bank and seed dispersal research for A. virginica and map populations before and after dam removal. Past research suggests A. virginica forms only a short-term seed bank that does not persist in buried or inundated soils. A survivorship model of buried seeds indicates maximum seed survival of eight years. Dispersal studies show that seeds leave populations floating on tidal streams, but the fate of these floating seeds is unknown. After dam removal, populations established on soils that had been covered by the dam or water for approximately 60 years. Hence, seeds can and do disperse from existing populations, float to unoccupied population sites, and establish populations. This knowledge will allow us to focus questions regarding the dynamics of re-established population sites. In addition, the results of this natural experiment show that A. virginica populations form metapopulations, in which the seed bank and seed dispersal jointly impact population extinction and re-establishment.