Having a wide range of tree and plant varieties on a landscape can help ensure long-term survival of that landscape. Landscapes with a high diversity of tree, shrub and perennials types tend to be less impacted by issues such as diseases, insect invasions, drought or other urban stresses. Many insects or disease attack one type of tree which can cause problems on a site. A landscape with nothing but ash trees, for instance, is an ecological and financial disaster. Having a mix of various trees types will help prevent major landscape losses.
It is common to see landscapes dominated by maple, ash and spruce trees. It makes sense long-term to blend in other tree species to increase diversity. Due to the invasion of Emerald ash borer to the Twin Cities, planting of ash trees should not be given any consideration. While maple trees provide value and brilliant fall color, it could be argued that maple trees have become over-planted in the Minnesota. Instead of planting a majority of maple trees on a site, blend in hackberry, swamp white oak, or disease-resistant elm trees. To increase the diversity of landscapes dominated by spruce trees, plant more fir, pine, tamarack, or red cedars.