Washington state is home to seven types of ecosystems and more than 3,000 native plants. The best way to identify state plants, as well as weeds and invasive species, is to purchase a comprehensive plant guide. A helpful resources is "Washington State Trees and Wildflowers: An Introduction to Familiar Species. " Additional information can be found at local extension offices such as the Washington State University Extension.
Washington is 360 miles from east to west and 240 miles from north to south. The state includes numerous mountain ranges, islands, river basins and prairie landscapes. Specific ecosystems include alpine, subalpine, mountain, ponderosa, shrub-steppe, rain shadow and west lowland forests. Each landscape includes particular native plants and weeds.
The state gets its nickname from its large number of evergreen trees. The state tree, the western hemlock, has soft, flattened, green needles and can grow to 60 feet. Rhododendrons, the state flowers, grow in shady, moist ecosystems and are a favorite in home gardens. They have dark green, leathery leaves and bloom in a variety of colors, primarily on the Pacific Coast. Douglas fir trees are also native to Washington. They have blue-green to dark green foliage with 1-inch long needles. When they're young, they grow in a pyramid shape, which becomes less pronounced as they age.
A weed is a plant that has the capability to reproduce in great quantities, competing and even threatening the survival of other native species. Common Washington weeds include everything from horsetails to ferns to sedges. The Washington State University Extension office has published "Weeds of the West," a full-color guide to identifying the state's weeds.
Invasive weeds are plants not native to Washington. They endanger native plants because they tend to have few natural threats to control their reproduction. Invasive weeds can impact a region's natural biodiversity, reduce crop yields and can be toxic to animals and people. Washington is working to manage many invasive weeds, including several species of thistle, scotch broom, English ivy and Himalayan blackberry. The Oregon State University Extension office has published "Pacific Northwest's Least Wanted List: Invasive Weed Identification and Management" as a resource for identifying and controlling invasive weeds.
Many plants in Washington are considered rare because they are endangered, threatened or near extinction. The list of rare state plants includes species of trillium, daisy, larkspur and raspberry. The University of Washington Botanic Gardens maintains a list of rare state plants, complete with photos to assist in identification.