What counts as an invasive tree species in California?

Invasive trees are non-native trees that spread aggressively and cause ecological, economic, or safety impacts. In California, 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 California-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 California?

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.

California Invasive Tree Species: Identification, Reporting & Control Resources

California Quick Links (Start Here)

These are the fastest paths to “Is this invasive here?” and “Who should I tell?”

National hub

Invasive Tree Species (Weed Trees) — definitions, red flags, and prevention.

Cal-IPC Inventory

Inventory categories and Plant profiles.

CalWeedMapper

Map distributions and prioritize management by region.

Tip: before you remove a tree, confirm ID. Some invasive trees look like natives or beneficial ornamentals. Incorrect removal is costly — and sometimes illegal if you mis-handle regulated plant material.

Commonly Tracked Invasive Trees in California

California’s invasive lists vary by region and habitat. Below are examples you’ll see frequently in inventories and mapping tools. Always confirm by location and program guidance.

Example	Why it’s a problem	Best next step
Tree-of-heaven (Ailanthus altissima)	Fast spread, strong resprouting, and can dominate disturbed areas.	Verify with Cal-IPC profile; plan treatment that stops resprouting (don’t just cut).
Giant reed (Arundo donax)	Major impacts in riparian corridors; can outcompete native willows and alter water dynamics.	Check riparian guidance; prioritize preventing fragment spread.
Tamarisk / saltcedar (Tamarix spp.)	Invades waterways and floodplains; changes habitat structure and hydrology.	Confirm species and site sensitivity; coordinate with local managers in riparian zones.

For more species, use Cal-IPC’s Plants A–Z and generate a localized report with CalWeedMapper.

Verify & Report: A Simple California Workflow

The best reports include clear photos and a precise location. The best control plans include follow-up.

1) Photograph

Leaves, bark, flowers/fruit, full canopy. Note habitat and whether seedlings are present.

2) Confirm ID

Use trusted profiles: Cal-IPC plant profiles.

3) Check presence

See if it’s established in your area using CalWeedMapper.

4) Report

Submit sighting info through local programs or map/reporting tools (include photos + location).

5) Plan control

Match treatment to the species and site. Avoid spreading seeds or fragments during removal.

6) Follow up

Re-check for resprouts and seedlings. Most invasive trees require multiple visits.

High-risk sites: riparian areas, disturbed lots, road edges, and post-fire landscapes. If the tree is near water or within sensitive habitat, coordinate before you act.

Control Playbook: What Usually Works (and What Usually Fails)

Most invasive tree control fails for one reason: the tree comes back. Plan control around preventing resprouting and new seedlings.

Don’t “cut and walk away”

Many invasives resprout aggressively when cut. A one-time cut can create a thicket.

Dispose carefully

Seeds and fragments spread. Bag seed heads, avoid hauling loose material, and follow local rules.

Time it

Some treatments work best when the plant is moving resources to roots. Follow species guidance.

Want a national overview of invasive “weed trees” and prevention strategy? Go back to: Invasive Tree Species.

California Invasive Trees FAQs

Where should I start if I’m not sure the tree is invasive?

Start with photos and a trusted profile. In California, Cal-IPC plant profiles and regional mapping tools are a strong first pass.

Is every “non-native” tree invasive?

No. Many non-natives are not invasive. “Invasive” means it spreads and causes harm (or is likely to) in natural areas.

Do invasive trees always need herbicides?

Not always, but many invasive trees resprout after cutting. The safest, most effective approach depends on the species and site. Follow label directions and local guidance.

California Invasive Tree Species

Softwoods

Hardwoods

Calculators

Resources

Programs