Efforts to replant tallgrass prairies in post-agricultural fields has been successful at restoring the dominant native prairie plants, but less successful at restoring the original plant diversity. There are a subset of prairie plants that are particularly difficult to re-establish in restorations. We postulated that the re-establishment of these plants is limited by the degradation of the soil community. We tested whether the re-establishment of prairie in post agricultural old fields can be accelerated by inoculation with remnant prairie soil and with arbuscular mycorrhizal (AM) fungi. AM fungi are one component of the soil community that typically promotes plant growth. Through a series field trials at The Nature Conservancy's Kankakee Sands Restoration Project and greenhouse experiments at Indiana University we found that the more difficult to establish plant species grew significantly better with prairie soil communities and with AM fungal inoculation. The response of weeds and prairie plants that readily establish in restorations were quite variable in their response to inoculation. Some plants grew significantly better with inoculation, others showed no difference in growth, while other plants had significantly lower biomass with inoculation. In field trials, we found greater diversity of native prairie plants in plots inoculated with prairie soil communities. These studies indicate that restoration of native diversity of prairie plants can be improved by re-establishment of the native soil community.