Washington State, often called the “Evergreen State,” boasts a remarkably diverse and abundant tree population. Its varied climates, from the wet Pacific coast to the arid eastern plains, foster a rich tapestry of forest ecosystems. These forests contribute significantly to the state’s scenic beauty, ecological health, and support wildlife.
Washington’s Iconic Conifers
Coniferous trees are a defining characteristic of Washington’s landscape, with several prominent species dominating its forests. The Douglas-fir (Pseudotsuga menziesii) stands as one of the most widespread and recognizable conifers, capable of growing over 85 meters tall and living for more than a thousand years. Its bark matures into a thick, deeply grooved, reddish-brown. Flat, pointed needles appear to stand out around the twig, and its cones are distinctive with three-pronged bracts.
Another prevalent species in Washington’s western forests is the Western Hemlock (Tsuga heterophylla). This large tree can reach 30 to 50 meters in height and typically lives for about 500 years. It is identified by its narrow crown with drooping new growth and feathery foliage from unequal-length needles. Its needles are flat, glossy, and soft, appearing yellow to dark green on the upper surface and whitish underneath. Western Hemlock is shade-tolerant, making it a common understory tree in dense forests.
The Sitka Spruce (Picea sitchensis) thrives in cool, moist climates near the Pacific Ocean, often reaching heights of 40 to 70 meters. It has an open crown with pendulous branches. Its stiff, sharp, blue-green needles are borne on small woody pegs. The bark is greyish-brown and tends to flake off in round scales.
Western Redcedar (Thuja plicata) is another significant conifer, growing up to 60 meters tall and sometimes living for a thousand years. It features a rapidly tapering trunk and an often irregular crown. Its bark is grey and stringy, easily tearing off in long strips. Its scale-like leaves are arranged in flat, fan-like sprays and emit a distinctive aroma when crushed. This tree is resistant to decay and insect damage, contributing to its longevity.
Washington’s Notable Deciduous Trees
While conifers largely define Washington’s forests, several deciduous trees contribute to the state’s ecological diversity, particularly in riparian zones and disturbed areas. The Bigleaf Maple (Acer macrophyllum) is the largest maple species in North America, with some individuals reaching up to 36 meters in height. It is recognized by its exceptionally large leaves, featuring five deep lobes and a shiny dark green surface that turns vibrant yellow in the fall. Older trees often host mosses, lichens, and ferns on their greyish-brown, shallowly grooved bark.
Red Alder (Alnus rubra) is a fast-growing deciduous tree commonly found in the Pacific Northwest, typically reaching 15 to 25 meters tall. Its smooth, thin, grey bark often has patches of white lichens and develops a rusty red color when bruised or scraped. The leaves are wavy and toothed, turning yellow before falling in autumn. Red Alder fixes nitrogen in the soil through a symbiotic relationship with bacteria in its roots, enhancing soil fertility for other plants.
The Pacific Madrone (Arbutus menziesii) is a distinctive broadleaf evergreen tree, growing 25 to 38 meters tall. Its most striking feature is its smooth, reddish-brown bark that peels away in thin strips during summer, revealing a smooth, greenish-yellow inner bark. The leaves are thick, broad, waxy, and dark green. In spring, it produces clusters of small, white, urn-shaped flowers, followed by bright red, bumpy berries in the fall.
Tree Distribution Across Washington’s Landscapes
Washington State’s varied geography and climate directly influence the distribution of its diverse tree species. Western Washington, characterized by abundant rainfall and proximity to the Pacific Ocean, supports dense, lush coniferous forests. This region, west of the Cascade Crest, is dominated by moisture-loving species like Douglas-fir, Western Hemlock, and Sitka Spruce, with the latter thriving particularly in outer coastal areas. Deciduous trees, such as Bigleaf Maple and Red Alder, are also common, especially in lowland riparian zones and disturbed areas.
Moving eastward, the Cascade Mountains create distinct ecological zones influenced by elevation and precipitation. As elevation increases, tree species transition to those adapted to colder temperatures and deeper snowpacks. Eastern Washington, situated in the rain shadow of the Cascades, experiences a drier, more continental climate. This region supports tree species tolerant of arid conditions, with Ponderosa Pine widespread and defining the lower treeline where forests meet shrub-steppe and grasslands. Douglas-fir is also present in eastern Washington in areas with more moisture, while Quaking Aspen is common in higher elevations and cooler, moister pockets.
Key Features for Tree Identification
Identifying trees involves observing several distinguishing features. Leaves are often the most obvious characteristic to examine, whether needle-like or broad. If broad, their shape, margin (smooth, toothed, or lobed), and arrangement on the twig (alternate, opposite, or whorled) are key. Observing whether a tree retains its leaves year-round (evergreen) or sheds them seasonally (deciduous) is also fundamental.
Bark texture and color also provide important identification cues. Features such as smooth, deeply furrowed, scaly, or peeling bark offer distinct indications.
Reproductive structures, including cones on conifers or fruits on deciduous trees, are highly specific identifiers. Their shape, size, and any unique attachments are valuable.
The overall shape or form of a tree, whether conical, rounded, or with a narrow crown, can also help narrow down possibilities. Twigs and buds offer additional details, especially during colder months. Understanding a tree’s typical habitat, such as preferred soil conditions, elevation, or proximity to water, can assist in accurate identification.