A List of the Trees and Shrubs of the Indiana Dunes State Park

Abstract

The Indiana Dunes State Park is located at Tremont, Porter County, Indiana, between LakeMichigan and the Chicago South Shore & South Bend Railroad and comprises 2182 acres. I have been listing the species of trees found in this park since 1935. The list of species of trees shown at the end of this article may be regarded as complete. The total number of species, 69, is of particular interest because it is probably greater than in any other woodland in the United States of similar size. The list of shrubs and woody vines includes those species that have come to my notice during the past few years. This list is not complete, especially in the genus Rubus, where there are three additional species that I have been unable to identify from the material collected, which does not fit any description in C. C. Deam's Flora of Indiana. In the list of tree species, the columns to the right of the name contain supplemental data. The four columns following the name show the dimensions of the largest individual in the park so far as measurements have been taken. Where a species has shown a tendency to increase or decrease in numbers, that fact is indicated in the next to the last column. Notes on the occurrence of species represented by very few individuals in the park are referred to in the last column and explained at the end of the table. The species shown in the tree list, found in this park, that are recognized as species of trees as distinguished from shrubs are those shown in the U. S. Forest Service's Check List of the Native and Naturalized Trees of the United States, issued in mimeograph form in 1944. In some cases, as explained in notes, the species do not attain tree size in this park. Quercus velutina is the most common tree of the sand hills, and Acer rubrum is probably the most common tree of the lowlands. The Red Maple is more common here than in any other woodland that I have explored. A large area of the marsh extending from the center of the park to the eastern border is treeless, but is covered with an impenetrable shrubby growth of dogwoods, blackberries, raspberries and grapevines. Seven species very common in Cook County, Illinois-Juglans nigra, Quercus macrocarpa, Quercus ellipsoidalis, Celtis occidentalis, Crataegus mollis, Rhus glabra and Acer negundo-are not found in this park. The reasons for their absence are worthy of investigation and comment. The sandy soil probably inhibits the growth of Juglans nigra, Quercus nmacrocarpa, Celtis occidentalis, Rhus glabra and Acer negundo, all of which range widely. The sand left by the ice sheet in this region was of the silica