Common trees of Wisconsin include four oaks—bur, black, white, and red—along with black cherry and hickory. Jack, red, and white pine, yellow birch, eastern hemlock, mountain maple, moosewood, and leatherwood grow in the north, with black spruce, black ash, balsam fir, and tamarack concentrated in the northern lowlands. Characteristic of southern Wisconsin's climax forests are sugar maple (the state tree), white elm, basswood, and ironwood, with silver maple, black willow, silver birch, and cottonwood on low, moist land. Prairies are thick with grasses; bogs and marshes are home to white and jack pines and jack oak. Forty-five varieties of orchid have been identified, as well as 20 types of violet, including the wood violet (the state flower). In 2003, six plant species were threatened, including the eastern prairie fringed orchid, prairie bush-clover, dwarf lake iris, Pitcher's thistle, Fassett's locoweed, and northern wild monkshood.
White-tailed deer, black bear, woodchuck, snowshoe hare, chipmunk, and porcupine are mammals typical of forestlands. The striped skunk, red and gray foxes, and various mice are characteristic of upland fields while wetlands harbor such mammals as the muskrat, mink, river otter, and water shrew. The badger, dwelling in grasslands and semi-open areas, is rarely seen today. Game birds include the ring-necked pheasant, bobwhite quail, Hungarian partridge, and ruffed grouse; among 336 bird species native to Wisconsin are 42 kinds of waterfowl and 6 types of shorebird that are also hunted. Reptiles include 23 varieties of snake, 13 types of turtle, and 4 kinds of lizard. Muskellunge (the state fish), northern pike, walleye, and brook trout are native to Wisconsin waterways.
In 2003, nine animal species were listed as threatened or endangered in Wisconsin, including the bald eagle, Kirtland's warbler, Karner blue butterfly, Hine's emerald dragonfly, Higgins' eye pearlymussel, piping plover, and gray wolf. The Bureau of Endangered Resources in the Department of Natural Resources develops programs designed to aid the recovery of threatened or endangered flora and fauna.