Poison oak is not an oak but a low-growing deciduous shrub. Its stems and leaves contain urushiol, a natural oil that causes a severe skin rash any time of the year, even in the winter when the shrub has no leaves.
The plant is native to north America and as such has significant wildlife value: Birds like robins like the berries, songbirds feed on its berries during fall migration, and other birds feed on the insects that live on poison oak.
However, when poison oak pops ups in your yard, protecting yourself from its dangers should take precedence over any wildlife considerations. After proper identification, it should be removed safely.
Familiarizing yourself with poison oak will also help you identify poison oak it in the wild so you can avoid exposure.
If poison oak pops up in your yard, it was most likely brought there by birds who eat the berries. The plant that is visible to the eye grows slowly, but poison oak develops a large underground root system. Because it’s so dangerous to humans, it is crucial to identify and remove it as soon as it pops up.
|Botanical Name||Toxicodendron diversilobum|
|Common Name||Poison oak, western poison oak, Pacific poison oak|
|Mature Size||Three to six feet height|
|Toxicity||Toxic to humans if touched|
Identification of Poison Oak
Poison oak belongs to the same genus as poison ivy and poison sumac, and it has similar botanical characteristics.
Like poison ivy, a single leaf consists of three leaflets, or three-parted leaves.
The stem of the center leaflet is longer than the stem of the leaflets on either side. Not all leaves are equally lobed, but when they are, they resemble oak leaves, which gives the plant its common name. The size of the leaves varies even on the same plant; the average leaf length is about six inches.
The new leaves in the spring are reddish, and because of the oil they contain, appear shiny. Later the leaves turn green. In the fall, before they drop, they turn into different shades of red and yellow.
Also, both the stems and the leaflets of poison oak are covered with fine hairs.
The clusters of small, white-greenish flowers in late spring turn into small, waxy, greenish-yellow or white berries in late summer. The berries often remain on the plant through early winter.
During dormancy, without the characteristic leaves, poison oak is much more difficult to identify. The stems are light brown, cinnamon-colored, or grayish, with an upright growth pattern, like sticks.
Where Poison Oak Is Found
Pacific poison oak is mostly found in the western United States, from Washington to California. It grows in woodland, grassland, hillsides, and coniferous forests but also along roadsides, in abandoned farm fields, and wasteland.
In full sun, poison oak is a dense shrub whereas in shady locations, it grows as a vine, reaching for the light and clinging onto trees or other vertical support.
Never burn poison oak. The toxic oils are released into the air through the smoke particles.
How to Remove Poison Oak
There are two different ways to remove poison oak: manually, or with herbicides. The advantage of manual removal is that you can do it any time during the year, whereas herbicide applications need to be timed according to the growing stage of the plant.
Types of Poison Oak
Atlantic poison oak (Toxicodendron pubescens) is native to the southeastern United States. It’s the eastern counterpart of the Pacific poison oak. Everything about the toxicity of Pacific poison oak also applies to the Atlantic poison oak.
Poison Oak Management Guidelines--UC Extension