Balsam fir, white spruce, paper birch, aspen, and mountain ash are typical boreal forest trees that grow along Isle Royale's rugged shoreline. Here, Lake Superior creates cool, moist conditions which favor boreal forest. In contrast, the warmer/drier conditions and deeper soils found in the interior of the island near its western end support an extensive forest of Northern hardwoods. There, autumn hikers along the Greenstone Ridge Trail shuffle through colorful leaves fallen from sugar maples and yellow birches, the two tree species that dominate this forest type. In fact, one location on this part of the island, Sugar Mountain, was once home to an Ojibwe maple sugaring camp in the 1840's. Nearby Red Oak Ridge is a reminder that northern red oak trees also make the western, interior part of the island their home.
In the island's low areas, visitors walk on boardwalks through swamp forests of northern white cedar, black spruce, tamarack, red maple, and black ash. Three species of pine trees (jack, red, and white) prefer drier feet and are limited to the island's rockier, more open sites.