Norway maple has escaped cultivation and invades forests, fields, and other natural habitats. It forms monotypic stands that create dense shade and it displaces native trees, shrubs and herbs. It can be identified from the similar native sugar maple by crushing the leaves. The crushed leaves will have a milky sap. Note - Do not buy, sell, or plant Norway Maple.
In 100 Years of Change in the Distribution of Common Indiana Weeds by William and Edith Overlease (2002) reported that Norway maple was not recorded in Indiana in 1899 (Coulter’s Catalogue of Indiana Plants) or in 1940 (Deam’s Flora). In 2002, Overlease observed it spreading and seeding in with many trees reaching maturity. Overlease recorded that Norway maple had spread in all 62 counties in Indiana: Adams, Allen, Bartholomew, Benton, Blackford, Boone, Brown, Carroll, Cass, Clinton, Dearborn, Decatur, DeKalb, Delaware, Elkhart, Fountain, Franklin, Fulton, Grant, Hamilton, Hancock, Hendricks, Henry, Howard, Huntington, Jasper, Jay, Johnson, Kosciusko, LaGrange, Lake, La Porte, Madison, Marion, Marshall, Miami, Monroe, Montgomery, Morgan, Newton, Noble, Owen, Perry, Porter, Pulaski, Putnam, Randolph, Ripley, Rush, St. Joseph, Shelby, Starke, Steuben, Tippecanoe, Tipton, Union, Vermillion, Wabash, Wayne, Wells, White, and Whitely. Overlease also found Norway apple in Huntington County however it was planted and not reproducing by seed.