Little Calumet Headwaters Nature Preserve is a 108-acre tract of woodland and wetland areas that comprise the headwaters of the Little Calumet River in northwestern Indiana. The preserve, consisting of upland hardwood forests, groundwater seeps, and wetland complex, is an area of high diversity due to its topographical variation. A floristic inventory, plot sampling, and seed bank analysis were used to determine the structure and composition of the plant communities. The flora consists of 298 species (27 exotic) representing 188 genera and 84 families. Dominant vegetation of the forest includes Liriodendron tulipifera, Prunus serotina, Packera aurea and Podophyllum peltatum. Each groundwater seep contains similar plant communities with variant species that depend on water flow and topography. They include species such as Symplocarpus foetidus, Impatiens capensis, and Caltha palustris and lack an extensive woody overstory except for occasional Salix spp. or Cornus spp. The wetland complex contains three distinct areas: an open fen dominated by Leersia oryzoides and Cornus spp.; a marsh dominated by Typha latifolia and Carex lasiocarpa; and a shrub-carr portion dominated by Symplocarpus foetidus, Cornus alternifolia, and Salix nigra. A wetland seed bank study resulted in a total of 46 species representing 33 genera and 22 families. A similarity of 71.7% was determined between the seed bank samples and the above-ground vegetation. The entire preserve has a high floristic quality index (FQI) of 70.1 and average mean coefficient of conservatism of 4.1. The high FQI value is influenced by property size and the number of communities in the preserve.