Oakleaf hydrangea’s year-long parade starts in spring when dark green leaves unfurl. Depending on the variety, the oak-like leaves can grow up to 12 inches wide. Flower buds form long, cone-shaped clusters that crown summer landscapes with color. The elegant clusters combine large, showy florets with small, budlike flowers. Unlike mophead hydrangeas, soil pH doesn’t affect the color of oakleaf blooms.