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Poison oak

Toxicodendron diversilobum

Updated Jan 27, 2024

Make a Positive Identification

Poison oak is a woody shrub or vine that grows in woodlands and grassy hillsides. In drier locations it grows in chaparral.
The leaves have three leaflets ranging from smooth edges to lobed, and are often shiny.
In the fall the leaves turn bright red. Poison oak loses its leaves in the winter.

Touching poison oak leaves or stems causes skin irritation, rash, and itching (dermatitis) on most people. Touching contaminated clothes, tools, and pets also results in a reaction.

Burning poison oak plants releases oil in the smoke. Don’t breathe smoke from burning poison oak plants. Severe irritation of the mouth, throat, and lungs may result.

After working or traveling in an area with poison oak, take steps to minimize exposure to the oil:
     Wash your skin to remove the oil as soon as possible after exposure to poison oak.
     Remove clothes and shoes and wash them separately from other clothing.
     Wash tools and pets that come in contact with poison oak plants.
     Soap and plenty of cold running water work to remove the oil from your skin. A solvent like isopropyl alcohol also works.
     A product called Tecnu® Skin Cleanser effectively washes away poison oak oil from your skin, pets, clothes, and tools.

Poison oak

Species: Poison oak

Joseph M. DiTomaso, University of California - Davis, Bugwood.org

Poison oak can grow in the form of a woody shrub.

Species: Poison oak

Joseph M. DiTomaso, University of California - Davis, Bugwood.org

It grows as a vine on trees and structures. The vines can also run along the ground.

Species: Poison oak

"Pacific poison oak (Toxicodendron diversilobum)" by Franco Folini is licensed under CC BY-SA 2.0

The leaves of poison oak alternate along the stem. They have three leaflets that can have smooth or lobed edges. The leaves are often shiny. They are purplish brown when they first emerge. They turn green when fully developed.

Species: Poison oak

Joseph M. DiTomaso, University of California - Davis, Bugwood.org

In the late summer and fall, leaves turn orange and red.

Species: Poison oak

"Poison Oak Berries" by jacki-dee is licensed under CC BY-NC-ND 2.0

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Poison oak Benefits

Poison oak is a natural part of the environment. Birds eat the berries. It provides habitat for animals.

Poison oak Risks

Touching poison oak leaves or stems causes dermatitis on many people.
Contact with contaminated clothes, tools, or pets will cause a reaction.
Burning poison oak plants releases oil in the smoke. Don’t breathe smoke from burning poison oak plants. Severe irritation of the mouth, throat, and lungs may result.

Risk Card

Does it cause harm?

Adults & Children

High

Property

Low

Pets

High

Annoyance

High

Environment

Low

Action Optional

Take Action?

If you have poison oak growing on your property in a place where you can’t tolerate it, take action to control it.

Do I need to take action?
It depends. Consider controlling it near homes and recreational areas. Otherwise, leave it alone.

What if I do nothing?
Poison oak seeds are spread by birds, and it will continue to grow where it is.

NEED HELP?

Consider a licensed pest control company. Learn How to Hire a Pest Control Company.
Your local Extension Specialist in Oregon and other states can suggest other methods.

Solutions for Poison Oak

Physically Remove Plants

Dig out individual plants and small patches. Remove the roots. Allergic people should not handle poison oak.

Grazing by Goats and Sheep

Goats and sheep are used by land managers to control poison oak.

Herbicides (Weed Killers)

Herbicides effectively control poison oak when used according to the label instructions.

Monitoring and Follow-Up

Look for poison oak growth at any time of the year.
Managing large stands requires several years of follow-up monitoring and treatment.

Method	Does it work?	Is it safe?	Recommendation
A Physically Remove Plants	Effective	Moderate risk	Use if Necessary
B Grazing by Goats and Sheep	Effective	Low risk	Recommended
C Herbicides Triclopyr, Glyphosate and Imazapyr	Effective	Moderate risk	Use if Necessary
D If Using Herbicides, Protect Yourself & Minimize Risks
E Prevent Poison Oak

Physically Remove Plants

Non-Chemical Method

Weston Miller, Oregon State University

Physically Remove Plants

Use if Necessary

DIGGING OUT POISON OAK WITH HAND TOOLS

When handling poison oak use gloves and protective clothing.

Dig out individual plants and small patches. Remove the roots.

Does it work?	Effective
How much effort?	High effort Cut stems near the ground and dig out root crowns and rhizomes.
What's the risk?	Moderate risk Skin contact with poison oak can cause a painful, itchy skin reaction (dermatitis). Digging large stands of established poison oak plants creates significant soil disturbance. After digging out poison oak roots, regrade the soil and apply mulch. Take steps to prevent erosion as needed.
Possible risk of exposure or harm from chemicals	NONE

Poison Oak Removal Tips

Cut stems near the ground and dig out root crowns and rhizomes.
Be careful to manage your exposure to the oils present in all above ground parts of the plant.
Don’t burn the debris but let it compost in piles over a long time.
The oils can remain for a number of years in the debris depending on how quickly it decays.

Grazing by Goats and Sheep

Non-Chemical Method

Scott Bauer, USDA Agricultural Research Service, Bugwood.org

Grazing by Goats and Sheep

Recommended

Goats and sheep are used by land managers to control poison oak.

Does it work?	Effective Grazing is an effective way to reduce the poison oak canopy. Then the root crowns and rhizomes can be located and dug out or treated with herbicides. After livestock eat poison oak, the stems will grow new shoots.
How much effort?	Moderate effort
What's the risk?	Low risk Goats will eat desirable vegetation as well as poison oak.
Possible risk of exposure or harm from chemicals	NONE

Contact professional pest control companies with experience grazing goats to control poison oak. Or ask your Soil and Water Conservation District office for referrals.

"Poison oak lunch" by Alan Vernon is licensed under CC BY-NC-SA 2.0

Deer browse on poison oak, but won’t provide effective control.

Herbicides Triclopyr, Glyphosate and Imazapyr

Chemical Method: Use with caution

David Stephens, Bugwood.org

Herbicides Triclopyr, Glyphosate and Imazapyr

Use if Necessary

Herbicides that contain the active ingredients triclopyr, glyphosate, and imazapyr effectively kill poison oak when used according to label directions. Requires several years of effort and monitoring.

Does it work?	Effective Expect that poison oak will regrow from the roots after treatment with herbicides. Look for regrowth and retreat as needed.
How much effort?	Moderate effort
What's the risk?	Moderate risk Herbicides come with real risks. ALWAYS read the entire label front to back. Review instructions even for brands you know. Herbicides can run off your site into waterways and may harm wildlife. See How to Keep Pesticides Out of Waterways.
Possible risk of exposure or harm from chemicals	Using herbicides includes some amount of risk. The lowest risk comes with using alternative methods. You may be exposed to an herbicide if you: Get it on your skin Breathe it in Eat or smoke afterward without washing hands Touch or eat plants that are wet with spray (you, pets, or children) Bring it inside on your shoes or clothes Follow directions closely to reduce risk.

Natural resource management professionals use herbicide products containing triclopyr, glyphosate, and imazapyr. Used individually or in a mixture, these products are effective chemical treatments for poison oak.
Premixed products are available in hardware stores and garden centers.

Photo of herbicide label highlighting active ingredient triclopyr

Weston Miller, Oregon State University

A white box on this example product label highlights active ingredient triclopyr. Text on the label states “Kills completely - stumps and roots won’t grow.”

Triclopyr doesn't injure most grasses. It will damage other broadleaf plants. It is a good choice for treating poison oak growing next to desired grasses in lawn, pasture, & meadow areas.
The best time to treat poison oak with triclopyr is after the fruit has formed and before the leaves start turning red.

Triclopyr comes in two forms including ester and amine (shown in the photo). The ester form absorbs better into the leaves than the amine form. The ester form provides better control with a lower concentration of herbicide.

The ester formulations become a vapor when applied on hot days. The vapor can drift and damage nearby plants. Check the label for temperature limits.

Photo of herbicide label highlighting active ingredient glyphosate

Weston Miller, Oregon State University

A white box on the example label highlights active ingredient glyphosate. Text on the label states “Kills grass and weeds around flower beds, trees, shrubs....”

Glyphosate will damage most plants and grasses. Don’t let the spray contact plants you want to keep.

The best time to treat poison oak with glyphosate is after the fruit has formed and before the leaves start turning red.

Photo of herbicide label highlighting active ingredients glyphosate and imazapyr

Weston Miller, Oregon State University

White box on example product label highlights active ingredients glyphosate and imazapyr. Text on the label states “Kills and prevents weeds for up to 1 year”.
Products with imazapyr will kill most grasses and broadleaf plants. Don't let the spray contact plants that you want to keep.
The best time to treat poison oak with glyphosate is in the spring when the leaves fully expand. Or, treat from mid-August through the end of September.

Imazapyr stays in the soil. It may affect non-target plants whose roots grow in the sprayed area.

Herbicide Application Tips

Common herbicide application techniques include foliar, bare stem (basal bark) and cut stem.
The best time to treat poison oak depends on the herbicide you use.
Herbicide treatments are less effective if the plants are drought stressed.
Expect that poison oak will regrow from the roots after treatment with herbicides. Look for regrowth and retreat as needed.

Worker spraying herbicide on 2-3 foot tall foliage

James H. Miller, USDA Forest Service, Bugwood.org

Foliar (Leaves) Application

Spraying herbicide on poison oak foliage is only practical when it can be done without damaging nearby plants you want to keep.
A backpack sprayer is effective for treating small areas.
For extensive infestations start with a foliar application to kill the seedlings, saplings, and shoots. Then follow up with a basal bark or cut stump applications on the remaining stems. Or, wait and make additional foliar applications.

Diagram of basal-bark herbicide application technique

James H. Miller, USDA Forest Service, Bugwood.org

Basal-Bark Application

This works best for stems that are less than 6 inches in diameter.
Concentrated herbicide (oil soluble) is mixed with another ingredient (adjuvant), typically a seed oil.
The mixture is sprayed on stems from the ground to a height of 12–18 inches.
The plant absorbs the herbicide sprayed on the trunk. The herbicide moves to the roots.

Gloved hand spraying herbicide with dye on cut stump

Lyon Duong, UF/IFAS

Cut-Stump Application

Cut stems as close to the ground level as possible.
Remove sawdust and debris from the cut.
Apply concentrated herbicide to the area just inside the bark. This area has living tissue (cambium) that will transport the herbicide to the roots.
Apply herbicide as soon as possible after cutting the stem.
For cut-stump applications, triclopyr is more effective during the early summer. Glyphosate is more effective when applied from mid-summer to leaf fall.

If Using Herbicides, Protect Yourself & Minimize Risks

Chemical Method: Use with Caution

BrianLasenby, iStock

Why is it important to read herbicide labels?

They have detailed information on how to use the product correctly and legally.
They contain information on potential hazards of the product.
They provide instructions you should follow for poisonings and spills.
Following label instructions helps you to minimize the risks and maximize the benefits.

Key Herbicide Safety Tips

Read the entire label front to back.
Follow the instructions.
Review the instructions even for brands you know.
Only apply the product where the label says it may be applied.
Be precise in your application. More is not better.

The Label is the Law

ALWAYS read the label before using herbicide products. The label is a legal document that provides information on how to safely use the herbicide. This helps avoid harm to human health and the environment. Using an herbicide in off-label ways is illegal. It can result in legal enforcement actions.

READ THE LABEL & Follow Instructions
It has instructions to protect you and the environment.

Labels are different for every product and they often change over time.
Use a magnifying glass if needed.
Pay attention to CAUTION, WARNING, and DANGER statements.
Pay attention to the PRECAUTIONARY STATEMENTS.
The law states you must read and follow herbicide instructions.

Protect Yourself
Eye, skin & lung irritants

Wear the right protective gear. This often includes chemical-resistant gloves, safety glasses, a long-sleeve shirt, pants, socks, and shoes.
Mix outdoors or in a well-ventilated area.
Wash hands after mixing or applying, and before eating or smoking.
Take a shower immediately after handling herbicides.
Wash clothes worn while mixing or applying separately from other laundry.

Protect Children & Pets
Children and pets are at risk if they eat or touch the plants before it dries.

Keep them away during and after applying herbicides (read label for how long).
Remove toys and pet dishes from yard before applying.
Don’t track herbicide products into your home on shoes or clothes.

Protect Plants You Want to Keep

Glyphosate and similar herbicide ingredients damage both grass and broadleaf plants.
Minimize spraying of foliage, stems, exposed roots, or the trunks of desirable shrubs or trees to avoid harm.
Follow the label to avoid damaging the roots of trees and shrubs.

Protect Pollinators

Apply in the early morning or evening when bees are less active.
Kill weeds before they flower. Avoid spraying flowering plants.
Do not spray on bees or insects.

Avoid Wet, Windy, or Hot Weather
Use during favorable weather for best results.

Don’t spray when it’s raining or when rain is expected in the next 24 hours.
Wind causes spray to drift that can get on you and desired plants.
Herbicides may be less effective in hot weather if the target plants are moisture-stressed.
Some herbicides can turn into a vapor in hot weather and damage nearby plants.

Don’t Spray into Water

It’s illegal to apply herbicides in a stream or slow moving/wetland pool.
You need a product registered for aquatic areas. This includes waterways, ditches, drains, and other places where water collects.

Storage & Disposal

Store in a secure area away from children.
Don’t put unused herbicide products in the trash.
Never pour down any drain or waterway.
Take unused herbicides to a hazardous waste facility.

Call 1-800-CLEANUP (1-800-253-2687) to find out where to dispose of herbicides.

For the Portland metro region in Oregon, contact Metro’s Recycling Information. Call 503-234-3000, email or visit Metro’s website

More about:

About Using Pesticides on School Grounds in Oregon

If using pesticides on school grounds, there are special rules in Oregon. See School Integrated Pest Management (Oregon Department of Agriculture).