Three contrasting urban areas in Milwaukee County were sampled to determine the tree species reproducing and the habitats in which seedlings become established. Habitats most favorable for seedling establishment were shrub hedges and areas along fence lines or adjacent to buildings. Overall, elm and ash were the taxa most successful in establishing seedlings. In the Menomonee Valley, seedlings of boxelder and tree-of-heaven were most abundant with elm and ash close behind, while in Shorewood and Brown Deer, a great variety of seedlings was present. Elm, ash, boxelder, Norway maple, buckthorn, cherry and mountain ash were the most prevalent. Successful seedling establishment depends upon availability of sites that offer exposed soil for germination and temporary protection from disturbance.
Boyd, J. and F. Stearns. 1985. Natural tree reproduction in urban environments. 18(1): 14-21.