Sandstone glades in the Ozark highlands contain unique communities of vascular plants, including several species of conservation concern, as well as abundant communities of terricolous cryptogams—collectively termed biological soil crusts. Biological soil crusts have important ecological roles in grassland systems, such as preventing erosion and retaining soil moisture. Despite the conservation importance of sandstone glades, this ecosystem has received little scientific attention, and the drivers of plant diversity and soil crust prevalence in sandstone glades are poorly understood. In this study, we assessed relationships between soil crust cover and vascular plant species richness and tested whether dominance shifts from soil crusts to vascular plants along a soil gradient. Soil crust cover was negatively related to vascular plant species richness, and vascular plant richness increased (and crust cover decreased) with increasing soil organic matter. As soil organic matter increased, the proportion of perennial vascular plants in the community also increased. These results provide some of the first quantitative evidence for drivers of plant diversity patterns in Ozark sandstone glades and suggest that soil characteristics have an important role in structuring the distributions of plants and crusts in sandstone glades.