Western Allegheny Plateau

The Western Allegheny Plateau covers the hill country of western Pennsylvania, eastern Ohio, and West Virginia, centered on Pittsburgh and reaching toward Columbus and Charleston. Steep wooded slopes, narrow valleys, and acidic soils shape what grows, and a lot of this region is shaded rather than open. Natives like flame azalea, sweet azalea, twinleaf, and creeping phlox are woodland plants that do their best work in part shade, which suits yards sitting under mature trees.

Conditions: Acidic soils on steep wooded slopes, 38–45 inches of rain, cold winters and humid summers, and a great deal of shade.

Cities and areas: Pittsburgh, Columbus, Charleston, Wheeling, Zanesville, Steubenville.