Growing a diverse urban forest: Species selection decisions by practitioners planting and supplying trees

Many North American cities have set ambitious goals to increase their urban forests, as well as improving the diversity of the trees planted. Diversity considerations include both a larger range of species and an increased percentage of native species. However, it is unclear how the urban foresters and organizations involved in tree planting and supply make species selection decisions. This article explores the species selection process of several actors who are planting or selling trees in the city of Toronto, Canada. Researchers conducted interviews with, and surveyed landscape architects, non-profit organizations, retail nurseries, garden centers, and urban foresters to gain an understanding of decision-making related to tree species selection. Differences between the sets of actors were primarily related to neighboring tree species, native species status, and tree pests. The available tree supply influenced the type of species planted or sold, suggesting this may be the fundamental factor determining how species diversity goals are implemented. Additionally, contrasting decision-making criteria did not consistently result in different species being planted. This finding reaffirms that despite urban forestry goals being interpreted through different criteria, the resulting selections can still often lead to a diverse range of tree species planted.