Native plant choices and invasive plants

Key Pacific Northwest Native Plant Species

Native plants have co-evolved with Oregon's climate and soils. Once established (over a species- and site-dependent period), native species offer exceptional resilience, drought adaptation, and ecological value for municipal and commercial landscape installations.

Profiles of 8 Essential PNW Native Species

1. Douglas-fir (Pseudotsuga menziesii): Oregon's official state tree. Massive evergreen conifer reaching 100 to 250+ feet. Fast-growing with root architecture influenced by soil and site conditions in well-drained soils. Intolerant of poorly drained, anaerobic, waterlogged clay soils. Dominant canopy species throughout Western Oregon.
2. Western Redcedar (Thuja plicata): Large evergreen conifer (80 to 150+ feet) featuring scale-like, aromatic foliage sprays and fibrous cinnamon-red bark. Highly shade tolerant. Naturally inhabits moist bottomlands, stream banks, and ravines. Increasingly suffering from severe dieback in urban Willamette Valley sites due to consecutive extended summer droughts.
3. Vine Maple (Acer circinatum): Deciduous small tree or multi-stemmed shrub (15 to 25 feet). Renowned for brilliant orange-scarlet autumn foliage. Naturally adapted to moist forest understories in partial to full shade. Susceptible to leaf scorch and dieback when placed in full afternoon sun or against reflective masonry walls.
4. Pacific Dogwood (Cornus nuttallii): Deciduous small-to-medium understory tree (20 to 40 feet) displaying large, showy creamy-white flower bracts in spring and red autumn fruit. Requires well-drained, acidic, organic-rich soil. Highly susceptible to Dogwood Anthracnose (Discula destructiva), especially when planted in stagnant, dense shade.
5. Tall Oregon Grape (Mahonia aquifolium / Berberis aquifolium): Oregon's official state flower. Stiff, upright evergreen shrub (3 to 6 feet) with spiny, pinnately compound, holly-like leaves that turn bronze-purple in winter. Produces vibrant yellow spring flower clusters followed by glaucous blue-black tart berries. Extremely drought-tolerant once established; pest resistant; thrives in sun or shade.
6. Salal (Gaultheria shallon): Dense, creeping-to-erect evergreen shrub (2 to 6 feet) in the heath family (Ericaceae). Features glossy, leathery ovate leaves, urn-shaped pinkish-white flowers, and edible purple-black fruit. Thrives in acidic, humic, woodland soils; excellent for slope erosion control in coastal and western forest settings.
7. Western Sword Fern (Polystichum munitum): Robust, evergreen clump-forming fern (2 to 4 feet tall and wide) with deep green, arching pinnate fronds. Foundational groundcover of the PNW forest floor. Highly drought-tolerant once established; thrives in moist or dry shade; binds slope soils against winter erosion.
8. Kinnikinnick / Bearberry (Arctostaphylos uva-ursi): Prostrate, mat-forming evergreen groundcover (6 to 12 inches tall, spreading 3 to 6 feet). Small leathery leaves, delicate urn-shaped pink-white blossoms, and bright red berries. Thrives in sandy, gravelly, low-fertility, acidic soils in full sun. Exceptionally drought-hardy; ideal for roadway medians, dry rock gardens, and green roof installations.

Native Species Selection Matrix

Invasives and Noxious Weeds (ODA Prohibited Species)

The Oregon Department of Agriculture (ODA) Noxious Weed Control Program classifies non-native, invasive plant species under statutory authority (ORS Chapter 569). Noxious weeds degrade landscapes, destroy native biodiversity, increase wildfire fuel loads, and cause severe structural damage to civil infrastructure.

Oregon noxious weed lists

ODA uses A, B, and T designations to prioritize noxious weeds. A-listed weeds have limited occurrence or threaten entry; B-listed weeds are more widespread; T identifies priority targets for agency action. Quarantine and local control requirements must be read separately from these policy categories.

Check the current official list and rules before specifying, selling, moving, or disposing of material. Do not treat every category as one identical statewide owner-eradication mandate. Prevent spread through clean equipment, inspected fill, appropriate disposal, and follow-up control. ODA laws and lists.

Recognize important invasive plants

English ivy, Himalayan blackberry, Scotch broom, and Japanese knotweed are important landscape invaders identified in Oregon's noxious-weed materials. Ivy climbs and spreads across the ground, competing with other vegetation and complicating tree inspection. Blackberry forms thorny canes and persistent crowns and can root at cane tips. Control must address regrowth rather than only remove visible tops.

Scotch broom is a woody legume with green stems and yellow pea-like flowers; its persistent seed bank makes follow-up essential. Knotweed has jointed hollow stems and a rhizomatous growth system. Soil and plant fragments can spread it, so excavation and disposal require a planned method rather than casual tilling.

Identify species and current restrictions, select permitted control methods, protect desirable plants, and inspect afterward. Pesticide treatment must satisfy ODA credential and label requirements. Avoid unsupported universal claims about thousands of pounds of ivy load, exact rhizome depth, or a guaranteed seed-life number.