Washington State is home to a rich diversity of forest ecosystems, shaped by its unique geography and varied climate. From the moist coastal rainforests to the drier eastern plains and the towering Cascade Mountains, different environments provide suitable habitats for a wide array of tree species. This natural variation results in a landscape where both towering evergreen conifers and vibrant broadleaf deciduous trees thrive, creating distinct botanical communities across the state. The interplay of rainfall, elevation, and temperature dictates which trees flourish in specific conditions, contributing to Washington’s varied and extensive forest landscapes.
Iconic Coniferous Species
Douglas-fir, a prominent evergreen throughout Washington, is recognized by its thick, furrowed bark and soft, flat needles that grow all around the twig. Its cones are distinctive, featuring three-pointed bracts that resemble mouse tails extending from between the scales. Douglas-fir can reach impressive heights, with some old-growth trees exceeding 300 feet. It is abundant in both western rain forests and drier forests east of the Cascade crest, and these trees are widely used for lumber, plywood, and paper products.
Western Hemlock, Washington’s official state tree, is one of the most abundant trees in western Washington, Oregon, and British Columbia. It is identified by its short, flat needles of unequal length, which are dark green on top and whitish underneath, forming flat sprays. A key characteristic is its drooping top and small cones, typically under 1 inch long. Western Hemlocks thrive in moist, cool climates and are shade-tolerant, often growing in mixed coniferous forests alongside Douglas-fir.
Western Redcedar is known for its fragrant, reddish-brown, fibrous bark that peels in long strips. Its scale-like leaves are tightly pressed against the branchlets, creating a flattened, braid-like appearance in lacy sprays. The cones are small, resembling tiny wooden roses, and often remain on the tree for extended periods. This species is found along the coast, thriving in high rainfall areas and moist, well-drained soils.
Sitka Spruce typically has sharp, stiff, bluish-green needles, about 1 inch long, that encircle the twigs. Its bark forms plates, and the cones are pale and slender, up to 4 inches long. This tree is primarily found in coastal and lowland areas of Washington, flourishing in cooler, wetter conditions. It can live for hundreds of years and reach massive heights.
Grand Fir is a tall conifer with lustrous, glossy green needles that are typically two inches long, arranged horizontally on opposite sides of the twigs, giving the branch a flattened appearance. The needles have two white bands on their undersides and are often notched at the tip. Its cones stand upright on the branches and disintegrate at maturity, so they are rarely found intact on the ground. Grand fir is found in moist river valleys and dry rainshadow forests.
Common Deciduous Species
Bigleaf Maple is recognized by its exceptionally large, five-lobed leaves, which can span up to 12 inches across, making them the largest of any maple. The bark is often rough and covered with mosses, especially on older trees. In the fall, its leaves turn vibrant yellow. This tree is common west of the Cascades, often found along stream banks and in moist, shady areas.
Red Alder is a fast-growing deciduous tree with thin, smooth, and often grayish bark that may have patches of white lichens. Its leaves are oval-shaped with pointed tips and wavy, toothed edges. This species quickly colonizes recently cleared land and is often found in moist woods, along streambanks, and in disturbed or wet soils. Red alder is a pioneer species, improving soil fertility through nitrogen-fixing bacteria in its root nodules.
Pacific Madrone stands out with its twisting, reddish-orange bark that peels away in summer to reveal smooth, light green, younger bark underneath, which eventually turns golden. Its leaves are leathery, oval-shaped, glossy dark green on top, and remain on the tree year-round as it is a broadleaf evergreen. This tree is typically found on dry, sunny sites, such as bluffs above the seashore or rocky slopes, particularly in Western Washington. It has white, bell-shaped flowers and bright red, bumpy berries that ripen in the fall.
Quaking Aspen is distinguished by its smooth, greenish-gray bark, which can become dark gray and rough on older trees. Its leaves are round to ovate with finely toothed margins and have a flattened petiole, causing them to tremble or “quake” in the slightest breeze. These leaves turn yellows and oranges in the fall. In Washington, it can be found along wetlands, streamsides, lake shores, and in rocky, well-drained soils, often forming clonal stands.
Oregon White Oak, also known as Garry Oak, is the only native oak species in Washington. It is recognized by its leaves with rounded lobes and its thick, furrowed, light gray bark. This tree produces acorns and typically grows to 80-100 feet tall, living for 250-500 years. Oregon White Oak thrives on dry, rocky slopes and in open savannahs, primarily found on the west side of the Cascade Mountains in Washington.
Identifying Trees in Washington
Identifying trees in Washington involves observing several key characteristics. Leaves or needles provide important clues, including their shape, margin, and arrangement on the stem. For conifers, needle length, sharpness, arrangement, and color variations are distinguishing features.
Bark texture and patterns also offer a significant identification tool. Bark can be smooth, furrowed, scaly, or peeling in strips. Color variations in bark, such as reddish or cinnamon tones, also aid identification.
Cones and fruits are often unique to each species. Conifers produce various cone shapes and sizes, from small, rose-like cones to larger ones with distinctive bracts. Deciduous trees bear different types of fruits, such as winged seeds or acorns.
The overall shape and form of the tree, whether it has a pyramidal crown, a broad rounded head, or a drooping top, can also contribute to identification. Considering the general habitat where the tree is found, such as moist stream banks or dry slopes, provides further context. Field guides and mobile applications can also serve as useful tools.
Tree Distribution Across Washington’s Regions
Washington’s diverse geography directly influences the distribution of its tree species, creating distinct forest regions. 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 such as Douglas-fir, Western Hemlock, and Western Redcedar. Deciduous trees like Red Alder and Bigleaf Maple are also common in lowland riparian zones and disturbed areas.
The Cascade Mountains present varied environments influenced by elevation and differing precipitation patterns. Lower and mid-elevations on the western slopes support conifers like Douglas-fir and Grand Fir. As elevation increases, tree species transition to those adapted to colder temperatures and deeper snowpacks, such as Mountain Hemlock at higher altitudes. The mountain forest region offers diverse habitats, with tree species varying based on specific elevation and moisture levels.
Eastern Washington, located in the rain shadow of the Cascades, experiences a drier, more continental climate. This region supports tree species that tolerate arid conditions, with Ponderosa Pine being widespread. Douglas-fir is present in areas with more moisture, and Quaking Aspen is common in higher elevations and cooler, moister pockets. The eastern side also hosts species like Grand Fir in moist areas.