Ailanthus altissima
Railway tracks (like roads and highways) are often colonized by non-native invasive species. In North America, such species include trees such as Ailanthus altissima, Paulownia tomentosa, Siberian Elm, and Norway Maple, and invasive non-woody plants such as Japanese Knotweed and Phragmites. The railway tracks provide corridors along which these species can spread and thrive, even when the surrounding areas might be less hospitable to them.