Washington state is divided into two distinct climatic regions by the Cascade Range. West of the Cascades (zones 7b–9b) is the maritime Pacific Northwest: mild, wet winters; cool, dry summers; acidic soils derived from glacial till and volcanic material. East of the Cascades (zones 4a–7a) is semi-arid to arid: cold winters, hot dry summers, alkaline soils derived from basalt.
These are not two versions of the same climate — they are fundamentally different growing environments requiring different native plants.
Per Washington State University Extension, native plants for western Washington are often not suitable for eastern Washington, and vice versa. Gardeners need to select species native to their side of the Cascades.
Western Washington Native Trees (Zones 7b–9b)
Pseudotsuga menziesii (Douglas Fir)
Zones 4–8 | Full sun | Mature: 80–200 feet (forests); 40–60 feet in gardens in 50 years
Per Oregon State Extension, Douglas fir is the dominant timber tree of the Pacific Northwest and an ecologically critical species. It is too large for most residential lots at maturity but grows slowly enough in gardens that it provides shade and wildlife habitat for decades before becoming a maintenance concern. Massive wildlife value — cones feed crossbills and Douglas squirrels; the tree supports dozens of caterpillar species.
Acer macrophyllum (Bigleaf Maple)
Zones 6–9 | Full sun to part shade | Mature: 30–75 feet
Per Oregon State Extension, bigleaf maple is native throughout western Washington in moist woodland sites. The very large leaves (8–12 inches across) are distinctive. Outstanding fall color. Moss and ferns colonize the bark naturally in the Pacific Northwest's moist climate. Tolerates part shade and moist soils.
Alnus rubra (Red Alder)
Zones 5–8 | Full sun | Mature: 40–60 feet
Per Washington State University Extension, red alder is the most common native deciduous tree in lowland western Washington, native to moist sites near streams and disturbed areas. It is a nitrogen fixer. It grows rapidly (2–4 feet per year) but is short-lived (50–70 years). Excellent for quickly establishing a native planting.
Western Washington Native Shrubs
Mahonia aquifolium (Oregon Grape)
Zones 5–9 | Part shade to full shade | Mature: 3–6 feet
Per Oregon State Extension, Oregon grape (also called tall mahonia) is the state flower of Oregon and is native throughout western Washington. Evergreen, holly-like leaves, fragrant yellow flowers in early spring, and blue-purple berries consumed by birds. Outstanding for shaded sites with acidic, moist soils. Deer avoid it.
Gaultheria shallon (Salal)
Zones 6–9 | Part shade to shade | Mature: 2–6 feet
Per Oregon State Extension, salal is an evergreen native groundcover-to-shrub that dominates the understory of western Washington's coastal forests. Waxy dark green leaves, pink-white flowers in spring, dark berries in summer. Once established it is extremely low-maintenance and tolerates deep shade. Spreads slowly by rhizome.
Cornus sericea (Red-Twig Dogwood)
Zones 2–8 | Full sun to part shade | Mature: 6–12 feet
Per Washington State University Extension, red-twig dogwood is native to moist streamside habitats throughout Washington. The bright red stems are outstanding in winter. Tolerates wet soils. Renewal pruning (cut 1/3 of oldest stems annually) maintains the brightest stem color.
Philadelphus lewisii (Mock Orange)
Zones 4–8 | Full sun to part shade | Mature: 5–10 feet
Per Oregon State Extension, Lewis's mock orange is the state flower of Idaho and is native to eastern and central Washington. Intensely fragrant white flowers in June. Tolerates dry conditions east of the Cascades. Prune immediately after flowering.
Sambucus racemosa (Red Elderberry)
Zones 3–8 | Full sun to part shade | Mature: 8–15 feet
Per Washington State University Extension, red elderberry is native to moist forest edges and streambanks throughout western Washington. Clusters of small white flowers in April–May are followed by bright red berry clusters that are consumed by at least 50 bird species. The berries are toxic to humans when raw. Fast-growing; useful for wildlife plantings and screening. Tolerates seasonal wet conditions. Cut back hard every few years to maintain vigorous growth and manageable size.
Eastern Washington Native Plants (Zones 4–7)
Pinus ponderosa (Ponderosa Pine)
Zones 3–7 | Full sun | Mature: 60–100 feet
Per Washington State University Extension, ponderosa pine is the dominant native tree of eastern Washington's lower-elevation dry forests. Distinctive orange-plated bark on mature trees. Very drought-tolerant once established. A large tree for large lots; not suited to suburban yards in eastern WA.
Ceanothus velutinus (Snowbrush Ceanothus)
Zones 4–8 | Full sun | Mature: 3–7 feet
Per Washington State University Extension, snowbrush is native to dry forest openings and slopes throughout the Cascades and eastern Washington. White flowers in June. Nitrogen-fixing. Drought-tolerant once established.
Artemisia tridentata (Big Sagebrush)
Zones 4–9 | Full sun | Mature: 3–5 feet
Per Washington State University Extension, big sagebrush is the signature plant of the Columbia Plateau and eastern Washington's shrub steppe. Highly drought-tolerant, strongly aromatic. Absolutely not suitable for moist western Washington conditions where it develops root rot. This is the most emblematic plant of eastern WA gardens and natural areas.
Pseudoroegneria spicata (Bluebunch Wheatgrass)
Zones 3–8 | Full sun | Mature: 18–30 inches
Per Washington State University Extension, bluebunch wheatgrass is the climax grass of eastern Washington's native bunchgrass steppe and one of the most important native grasses for restoration and low-water landscaping east of the Cascades. Excellent drought tolerance; forms upright bunches with attractive seed heads. Used in lawn alternatives, roadsides, and naturalistic plantings. Dormant in summer; greens up with fall rains.
Penstemon speciosus (Royal Penstemon)
Zones 4–8 | Full sun | Mature: 12–24 inches
Per Washington State University Extension, royal penstemon is native to dry rocky slopes and sagebrush plains in eastern Washington. Large blue-violet flower spikes in May–June. Very drought-tolerant once established. Requires excellent drainage; dies in wet heavy soil. One of the showiest native perennials for dry-site gardens east of the Cascades.
What I'd do differently
I garden in zone 7a on Long Island, not the Pacific Northwest, so I have no personal experience with any of these plants in the ground. What I would pass on from reading the Extension literature: the single most common mistake gardeners in Washington make with natives is ignoring the Cascades divide. A plant that's a reliable workhorse in Olympia can be dead in Yakima by its second summer, and vice versa.
If I were establishing a native border on the west side, I'd start with the three most forgiving species — Oregon grape (Mahonia aquifolium), red-twig dogwood (Cornus sericea), and salal — and add more specific species once I had a sense of my site's drainage. West-side sites that look average often have much worse drainage than they appear, particularly in subdivisions built on compacted fill.
Frequently Asked Questions
How do I handle western Washington's wet winters when planting native shrubs? Per Oregon State Extension, most western Washington natives are adapted to the wet winters and will not require drainage amendment. The exceptions are plants from well-drained rocky sites (some native ceanothus, arbutus) — site these on slight slopes or berms to ensure drainage.
Are Pacific Northwest natives deer-resistant? Per Washington State University Extension, deer browse many native plants in western Washington, particularly in suburban areas where deer populations are high. Oregon grape, salal, and red-twig dogwood are moderately resistant. Vine maple, red alder, and native roses are frequently browsed.
Can I use native plants to replace lawn in eastern Washington? Per Washington State University Extension, replacing lawn with drought-tolerant native groundcovers and shrubs significantly reduces water use in eastern Washington's semi-arid climate. Native bunchgrasses (bluebunch wheatgrass Pseudoroegneria spicata, Idaho fescue Festuca idahoensis) and penstemons are effective low-water lawn alternatives for sunny sites.
Sources
- Washington State University Extension — Native Plants
- Oregon State Extension — Pacific Northwest Natives
- Missouri Botanical Garden — Plant Finder