Rolling surface of a glaciated plain in central Minnesota. Summers are hot, with frequent tornadoes. Most precipitation takes place during the growing season. Although other forests have oak and hickory, only this particular forest association has both species in abundance. From eastern Kansas to Indiana, it forms a mosaic pattern with prairie.
Widespread dominants are white oak, red oak, black oak, bitternut hickory, and shagbark hickory.
The understory is usually well developed, often with flowering dogwood. Other understory species include sassafras and hophornbeam. The shrub layer is distinct, with some evergreens. Many wildflower species occur. Wetter sites typically feature an abundance of American elm, tuliptree, and sweet gum.