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Photo Credit: Ryan McMinds, Flickr -
Photo Credit: Bri Weldon, Flickr -
Photo Credit: (c) Aaron I. Liston, courtesy of OregonFlora
Note: Poison oak is a native plant to the Pacific Northwest. It contains a toxic oil that causes severe skin irritation upon contact.
Also known as: Pacific poison oak, western poison oak
“Leaves of three, let it be. If it’s hairy, it’s a berry. If it’s shiny, watch your hiney.” This famous rhyme can help identify poison oak while exploring nature. While native to the Pacific Northwest, this plant contains a toxic oil that causes severe skin irritation for many people.
CAUTION: Avoid handling this plant, it is toxic! It contains a toxic oil that causes severe skin irritation upon contact.
Description:
| Life Cycle: | Perennial (life cycle lasts more than one year) |
| Early Detection and Rapid Response species: | No |
| Height: | When growing as a shrub, poison oak can reach 6 feet (2 meters) tall. When growing as a climbing vine, it usually grows 10 – 30 feet (3 – 9 meters) long but can grow up to 100 feet (30 meters). |
| Leaf Description: | Three dark green leaflets have lobed edges that resemble oak tree leaves. The leaf surface is glossy and can appear leathery in texture. Its leaves are deciduousTrees or shrubs that lose their leaves seasonally. and turn red before falling off in the fall. Its woody stems are brown and lack thorns which can help with identification. |
| Fruit & Flower Description: | Small, greenish-white flowers bloom in spring at the point where leaves meet the stem. Its seeds are contained in a small greenish-white fruit that ripens in August. |
| Bloom Time: | April to June |
Habitat:
- Poison oak grows in a variety of habitats from riparian areas to dry woodlands.
- The plant thrives in areas receiving full sunlight but can also grow in areas with full shade.
- It is commonly found in woodlands, pastures, riparian areasAreas that are directly adjacent to flowing streams, creeks, or rivers., and along hiking trails.
Impact:
- It is native to the Pacific Northwest and does not pose a threat to its natural ecosystems.
- However, the allergic reaction caused by this plant can lead to problems in areas frequented by people.
What you can do about it:
- Always remember to protect yourself from its toxic oil by wearing long sleeves, pants, and gloves.
- Hand pulling or digging plants out of the ground is easiest when the soil is damp from rain. In Washington County, fall through spring is a great time to manually remove it.
- Mowing is not an effective control for poison oak. Its roots will remain intact, and the plant can vigorously grow back.
Look-alikes:
When Oregon white oak (Quercus garryana) is small, it can be confused with poison oak due to the similarities in their leaves. Oregon white oak has leaves with far deeper lobes and do not grow in groups of three.
Poison oak is often confused with blackberry (Rubus species). Both plants have leaves that grow in sets of three, but blackberry has thorns that grow along its stem.
Noxious Weed Listing:
| State of Oregon: | Unlisted |
| State of Washington: | Unlisted |
More Resources:
Download the Poison Oak Best Management Practices factsheet
- Pacific Northwest Weed Management Handbook: Poison oak
- University of California, Weed Research & Information Center: Poison oak