More than 1,300 plant species have been identified in Washington. Sand strawberries and beach peas are found among the dunes while fennel and spurry grow in salt marshes; greasewood and sagebrush predominate in the desert regions of the Columbia Plateau. Conifers include Sitka spruce, Douglas fir, western hemlock, and Alaska cedar; big-leaf maple, red alder, black cottonwood, and western yew are among the characteristic deciduous trees. Wild flowers include the deerhead orchid and wake-robin; the western rhododendron is the state flower. In 2003, six plant species were threatened, including golden paintbrush, Nelson's checker-mallow, Kincaid's lupine, Spalding's catchfly, Ute ladies'-tresses, and water howelia. That year, four species were endangered, including Bradshaw's desert-parsley, showy stickseed, Wenatchee Mountains checkermallow, and marsh sandwort.
Forest and mountain regions support Columbia black-tailed and mule deer, elk, and black bear; the Roosevelt elk, named after President Theodore Roosevelt, is indigenous to the Olympic Mountains. Other native mammals are the Canadian lynx, red fox, and red western bobcat. Smaller native mammals—western fisher, raccoon, muskrat, porcupine, marten, and mink—are plentiful. The whistler (hoary) marmot is the largest rodent. Game birds include the ruffed grouse, bobwhite quail, and ring-necked pheasant. Sixteen varieties of owl have been identified; other birds of prey include the prairie falcon, sparrow hawk, and golden eagle. The bald eagle is more numerous in Washington than in any other state except Alaska. Washington is also a haven for marsh, shore, and water birds. Various salmon species thrive in coastal waters and along the Columbia River, and the octopus, hair seal, and sea lion inhabit Puget Sound.
Animals driven away from the slopes of Mt. St. Helen's by the volcanic eruption in 1980 have largely returned; more than 25 species of mammals and over 100 species of birds have been observed inhabiting the mountain again. The number of elk and deer in the vicinity was roughly the same as prior to the eruption although the mountain goat population reportedly had been killed off. Earlier, on 17 August 1982, the Mt. St. Helen's National Volcanic Monument was created by an act of Congress; it includes about 110,000 acres (44,500 ha) of the area that had been devastated by the original eruption.
In 2003, 30 animal species were listed as threatened or endangered in Washington, including the Columbian white-tailed deer, woodland caribou, short-tailed albatross, brown pelican, pygmy rabbit, humpback whale, nine species of salmon, and two species (green and leatherback) of sea turtle.