Mining wastes can pose environmental hazards. These hazards can be mitigated by promoting the growth of native plants that can stabilize the mine wastes and potentially toxic elements in situ (i.e., phytostabilization). We grew a widespread perennial grass species (Bouteloua curtipendula) in dolomite amended polymetallic tailings from a historic mine in southeastern Arizona (USA). We applied a compost top dressing and an endophyte seed coating alone and in combination to quantify improvements in plant growth and potentially toxic trace element stabilization. This release provides the data on the following: temperature, light, and humidity during growth; plant growth rates and biomass yields; organic matter concentrations in the tailings and compost layers; and major, minor, and trace elements in plant tissues, the compost layer, the tailings layer, and in water extracts of the tailings layer.