Forest and prairie mix in a transitional belt on the eastern border of the division. The prairie climate is not designated as a separate variety in the Koppen-Trewartha system. Prairies lie on the arid western side of the humid continental climate, extending into the subtropical climate at lower latitudes. Prairie vegetation is dominated by tall grasses associated with subdominant broad-leaved herbs. Trees and shrubs are almost totally absent, but a few may grow as woodland patches in valleys and other depressions.
Grasses are deeply rooted and form a continuous cover.
They flower in spring and early summer, with forbs appearing in late summer. Because there is less rainfall in the grasslands than in forest, there is also less leaching of the soil. The pedogenic process associated with prairie vegetation is calcification, as carbonates accumulate in lower soil layers. Soils of the prairies are Mollisols, which have black, friable, organic surface horizons and a high content of bases. Grass roots deeply penetrate these soils.