Vermont is in the temperate broadleaf and mixed forests biome. Much of the state, in particular the Green Mountains, is covered by the conifers and northern hardwoods of the New England-Acadian forests. Common trees of Vermont are the commercially important sugar maple (the state tree), the butternut, white pine, and yellow birch. There are 15 types of conifer, 130 grasses, and 192 sedges. There is such an abundance of flora in Vermont, with 2,000 higher plant species, that it was named the Green Mountain State and has some of the cleanest air and water in the United States.