Fraxinus quadrangulata, the blue ash, is a species of ash native primarily to the Midwestern United States from Oklahoma to Michigan, as well as the Bluegrass region of Kentucky and the Nashville Basin region of Tennessee. Isolated populations exist in Alabama, Southern Ontario, and small sections of the Appalachian Mountains. It is typically found over calcareous substrates such as limestone, growing on limestone slopes and in moist valley soils, at elevations of 120–600 m.

The Bluegrass region is a geographic region in the U.S. state of Kentucky. It makes up the central and northern part of the state, roughly bounded by the cities of Frankfort, Paris, Richmond and Stanford. It is part of the Interior Low Plateaus ecoregion.