A deciduous forest dominated by tall, slender oaks looks very different from one composed of wide-spreading beech trees and rich evergreen hemlocks. A prairie dominated by grasses is altogether different from a forest of stately trees. Within different plant communities a vast diversity of species is found. In a tallgrass prairie dominated by three grass species, you may find more than nine different grasses and up to three hundred different forbs. A mixed mesophytic forest may have over thirty different tree species, even though only two or three are codominant.
Ecological health depends on diversity.
Plant communities are naturally diverse, but our gardens are comparatively barren. A typical garden has one grass, bluegrass turf, a dozen perennial plants, three different shrubs, and one or two different trees. If we are to make our gardens as attractive to wildlife as they are to us, we must understand biological structure and put that knowledge to work. We must learn to appreciate both biological and visual complexity. In a forest, the dominant species is the tree that contributes the most cover to the canopy.