What counts as an invasive tree species in Washington?

Invasive trees are non-native trees that spread aggressively and cause ecological, economic, or safety impacts. In Washington, lists and inventories help identify which species are actively damaging natural areas and which are high-risk watch species.

Where can I verify whether a tree is considered invasive?

Start with Washington-focused inventories and plant profiles (such as Cal-IPC), then cross-check distribution in mapping tools and local extension or land management guidance.

Should I remove an invasive tree myself?

Small seedlings may be manageable, but many invasive trees resprout aggressively when cut. For larger trees, consult local guidance and consider a professional—especially near structures, waterways, or utility lines.

How do I report an invasive tree sighting in Washington?

Use regional reporting and mapping tools when available and include photos plus a precise location. You can also contact local invasive species programs, land managers, or extension offices.

What is the biggest mistake when controlling invasive trees?

Removing the top growth without stopping resprouting or seed spread. Successful control usually combines correct timing, follow-up monitoring, and safe disposal to prevent re-establishment.

Invasive Trees in Washington State (WA) – ID, Impacts, Control & Reporting

Washington’s invasive trees and woody invaders

Washington’s forests, parks, riparian corridors, and urban greenbelts can be heavily impacted by invasive trees and woody invasive shrubs that spread by seed, resprout after cutting, and form dense thickets. Use this page as a fast hub: identify what you’re seeing, learn the “do not spread” basics, and jump to official WA resources for reporting and best‑practice control.

Quick links for Washington (official)

Spot it fast

Don’t move cuttings, seed heads, or soil.
Photograph leaves, bark, flowers/fruit, and the whole plant.
Check county rules (some species are regulated or quarantined).

Pacific Northwest invasive species hub

Use Washington as your anchor page, then jump to neighboring state hubs for Oregon and Idaho. Many invasive trees spread along shared corridors (I‑5, Columbia & Snake River systems, rail lines, and disturbed edges), so verifying the right list and timing in each state matters.

Washington (WA)

Statewide hub + county resources, timing, and top woody invaders.

Open WA hub WA NWCB

Oregon (OR)

Reporting + noxious weed lists + state guidance for priority invasive trees.

Open OR hub Report (OR)

Idaho (ID)

Invasive plants + noxious weeds ID tools, maps, and program contacts.

Open ID hub Noxious weeds (ID)

PNW priority watch list (shared corridors): Tree‑of‑heaven, English holly, Norway maple, butterfly bush, Russian olive, and knotweeds often show up near transportation corridors, riparian edges, and disturbed construction zones.

Fast rule: if you cut a resprouting invasive (like Tree‑of‑heaven) without a plan, you often get more stems. Timing + follow‑up is the difference between “removed” and “multiplied.”

6 invasive woody species to know in Washington

These are common “watch list” candidates across many WA counties and restoration programs. Always verify identification with a local extension or noxious weed board before treatment.

Tree‑of‑heaven (Ailanthus altissima)

Fast growth, aggressive root suckers, and thicket‑forming habit; often spreads along disturbed corridors.

WA profile

English holly (Ilex aquifolium)

Shade‑tolerant evergreen that can invade forest understories and displace native regeneration.

WA profile

English hawthorn (Crataegus monogyna)

Thorny small tree that forms dense hedges and can spread into riparian and disturbed habitats.

WSU weeds hub

Cherry laurel (Prunus laurocerasus) invasive shrub/tree in Washington

Cherry laurel / English laurel (Prunus laurocerasus)

Evergreen hedge plant that can escape cultivation and dominate understory edges and slopes.

Learn more

Butterfly bush (Buddleja davidii)

Woody shrub that colonizes gravel bars and disturbed ground; spread concerns led to WA restrictions.

WA profile

Scotch broom (Cytisus scoparius)

Nitrogen‑fixing shrub that creates dense stands and changes habitat conditions for native plants.

Alternatives & info

What to do next in Washington

1) Confirm ID

Use multiple photos and compare to official fact sheets before you cut or treat.

2) Prevent spread

Bag seed heads, clean tools, and avoid transporting contaminated soil or mulch.

3) Use local guidance

County weed boards often publish the most practical timing and disposal guidance.

Invasive Trees in Washington State

Softwoods

Hardwoods

Calculators

Resources

Programs

Washington’s invasive trees and woody invaders

Quick links for Washington (official)

Spot it fast

Pacific Northwest invasive species hub

Washington (WA)

Oregon (OR)

Idaho (ID)

6 invasive woody species to know in Washington

Tree‑of‑heaven (Ailanthus altissima)

English holly (Ilex aquifolium)

English hawthorn (Crataegus monogyna)

Cherry laurel / English laurel (Prunus laurocerasus)

Butterfly bush (Buddleja davidii)

Scotch broom (Cytisus scoparius)

What to do next in Washington

1) Confirm ID

2) Prevent spread

3) Use local guidance

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