The Boundary Waters area is within the Laurentian Mixed Forest Province (commonly called the "North Woods"), a transitional zone between the boreal forest to the north and the temperate hardwood forest to the south that contains characteristics of each. Trees found within the wilderness area include conifers such as red pine, eastern white pine, jack pine, balsam fir, white spruce, black spruce, and white-cedar, as well as deciduous birch, aspen, ash, and maple. Blueberries and raspberries can be found in cleared areas. The BWCAW is estimated to contain of old growth forest, woods that may have burned but have never been logged. Before fire suppression efforts began during the 20th century, forest fires were a natural part of the Boundary Waters ecosystem, with recurrence intervals of 30 to 300 years in most areas.