The common saying "leaves of three, let it be" makes it easy to remember that poison oak leaves have three leaflets. The leaflets vary in size, shape and color but resemble scrub oak leaves. They are larger in the shade (up to 6 inches) than in the sun. Leaf margins are wavy and may have lobes. Early in the season, leaves are a bright, shiny green but turn yellow and red in the fall. Poison-oak has three main growth forms:
- An upright shrub.
- A ground-hugging shrub.
- A climbing, clinging vine.
Getting rid of poison oak
Poison oak will readily resprout if mowed or cut. The roots can be dug out in small areas with moist, loose soil. But avoid grubbing in dry or rocky soil because the roots break easily and will resprout from root fragments. Goats, sheep and other animals will browse poison oak, but the plants will come back.
Several types of herbicides can control poison oak. Specific recommendations will depend on your management goals and the type of property you are using them on. Look for products labeled for your property type with one of the following active ingredients.
- Glyphosate is most effective when applied late in the season when the leaves are still green but the plants have fruited.
- Triclopyr from spring to fall.
Repeat applications are likely necessary. Follow all label directions. You can spray the foliage or apply the chemical on freshly cut stems. For more information, search for poison oak in the quick find box at the bottom of the PNW Weed Management Handbook website for more information.
I'm starting to itch!
All parts of the plant — leaves, stems, roots, flowers (except the pollen) and fruits — contain the poisonous oil urushiol ("oo-roo-she-all"), which can cause a severe rash if it gets on the skin or is inhaled through smoke in the lungs.
Urushiol binds with skin proteins within 10–15 minutes, making removal difficult. A blistery, itchy rash can erupt within 24 to 48 hours and last for two to three weeks, or up to six weeks in the most susceptible individuals.
Wildland firefighters often develop poison oak or poison ivy rashes because the burning plants release billions of urushiol particles into the smoke, contaminating firefighters and their gear.
Removing poison oak oil
There are two options for removing the urushiol oil from your skin:
- Soap and water: Urushiol is like a resin, and heat and perspiration work as a vehicle to transfer it. Rinse with cool water and mild soap within 10 minutes after exposure. The effectiveness of this technique dissipates quickly, decreasing to 25% effectiveness at 15 minutes and 10% at 30 minutes. All the urushiol will absorb into the skin after 30 minutes of contact. Clean exposed clothing with soap and water in a laundry machine.
- Over-the-counter products: Multiple over-the-counter products are available to reduce urushiol reactions after exposure. Those shown to be effective in laboratory tests include Tecnu and Zanfel and the cleansers Goop and Dial Ultra dishwashing soap. However, more research would help tease out overall effectiveness.
Avoiding reexposure
Urushiol is potent and can stay active on various surfaces for a year. The most common spots for urushiol to lie in wait for reexposure are fingernails, clothing (especially wrists and cuffs), tools and equipment, and pets.
Use the above strategies to decontaminate your gear. Apply soap or ointment and rinse after each possible exposure.
- Apply directly onto the tool and wipe it down before and after use. Depending on the product used, porous, synthetic handles may be compromised, so test a small area before coating the item.
- Add the product to the wash when cleaning your exposed gear and clothing. Keep contaminated articles separate from other laundry.
Prevention
Urushiol spreads over the body by different means. Avoid these plants if at all possible. If not, treat your body and gear quickly after a potential exposure to reduce the severity and spread of the rash. Treating as much skin as possible the moment it is noticed (best is a full body wash in a shower) can dramatically reduce the severity of the reaction and contain the rash before it becomes fully realized.
Urushiol moves quickly through thin clothing, especially when sweating from exertion. Instead, wear dry, loosely woven clothing to keep the broken stems and leaves away from the skin. Urushiol cannot penetrate vinyl, which is the ideal fabric for gloves when working in poison-oak areas.
See more information in Pacific Poison-oak and Western Poison-ivy: Identification and Management.
