toxicodendron-diversilobumCommon name: poison oak

Scientific name: Toxicodendron diversilobum

Native American name: K’wan’-tee-tr’vt (Tolowa Dee-ni’)[1]

Plant family: Anacardiaceae

Description: T. diversilobum can grow as either a shrub or climbing vine. As a shrub it can grow from 1 ft to 9 or more feet in height.[2] Vines vary between 10-30 feet in length.[3] T. diversilobum features leaflets; each leaf features three pinnate leaflets, each between 3-7 cm and oval in shape. T. diversilobum leaves can resemble oak leaves, and as they share habitat with oaks, it is important to note this similarity.[3] Leaves are deciduous, and change color from green and greenish-red in the spring and summer to dark red in the fall. Male and female T. diversilobum flowers occur separately.  Furthermore, each individual has one sex of flower present.[2] Therefore, T. diversilobum cannot self-fertilize.[2] Flowers are inflorescent, white and grow from leaf axils,[4] and range from shades of white, green and yellow in color. They bloom in the spring.[5] T. diversilobum fruit are small white drupes, which are inedible to humans but are consumed by some birds and rodents.[6] These fruit bear in the summer and fall.[3] T. diversilobum vines spread themselves via roots and by working their stems into gaps.[3] Shrubs spread by rhizome activity. Seeds are dispersed by birds. Shoots can be used to propogate.[2]

T. diversilobum features a compound urushiol. Urushiol is an oily toxin, which can cause a range of allergic reactions upon skin contact.[2], [3] Contact with any part of the plant can result in a reaction, as all parts contain the toxin.[3], [5] Burning of the plant poses a special threat, as inhalation of urushiol can be deadly. [3], [5]

Habitat and range: T. diversilobum grows in a wide variety of climates and soil types. It grows in elevations less than 5,500 ft. It is moderately shade tolerant. T. diversilobum can be found flourishing in a variety of woodland and riparian habitats, as well as in mountainous habitat.[3] It also grows well on stream banks and in thicket.[5] Its adaptability and tolerance for varied habitat is evidenced by its status as the most abundant shrub in California.[3] However, T. diversilobum does require moist soil to thrive.[2] T. diversilobum is found throughout the Northwest, from British Columbia to Southern California.[6]. [7]

Historical and contemporary uses:

T. diversilobum had a variety of uses in the pre-European contact Pacific Northwest. Its branches were used, and still may be used as a basket-making material throughout central and southern California by a variety of tribes.[8]

[1] Bommelyn, Loren Me’-lash-ne. Taa-laa-wa Dee-ni’ Wee-ya’; Formerly published as Now You’re Speaking-Tolowa The Deeni people, their language.2nd Edition, 2006

[2] Plants For a Future Database. Plant Profile Rhus diversiloba – Torr.&A.Gray. Accessed via

[3] Forest Service Plant Database. Accessed via

[4] University of Washington’s Burke Museum of Natural History and Culture. Herbarium Database. Accessed via

[5] University of Texas at Austin Larry Bird Johnson Wildflower Center. Accessed via (

[6] United States Department of Agriculture Natural Resources Conservation Service Database. Plant Profile for Toxicodendron diversilobum. Accessed via

[7] UC Berkeley, Cal Photo Database. Accessed via

[8] University of Michigan-Dearborn Native American Ethnobotany Database. Accessed via query: Toxicodendron diversilobum.