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Toxicodendron diversilobum

Toxicodendron diversilobum (Torr. & A. Gray) Greene

Pacific Poison Oak, Western Poison Oak

Anacardiaceae (Sumac Family)

Synonym(s): Rhus diversiloba, Toxicodendron radicans ssp. diversilobum


USDA Native Status: L48 (N), CAN (N)

An erect or spreading shrub or a climbing vine with 3-parted leaves and brown or whitish berries. Western Poison Oak is not a true oak, but a close relative of Poison Ivy (Toxicodendron radicans). Poison Ivy also has 3-part compound leaves, but the leaflets are not lobed and have more slender, pointed tips. Poison Ivy replaces Poison Oak east of the Pacific Coast region. Poison Oak is so widespread and common in California that it almost qualifies as the state shrub. Anyone spending time in the lowlands and foothills of the state should learn to recognize the plant and avoid it at all costs. Livestock and deer commonly browse the plant without ill effect.


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Plant Characteristics

Duration: Perennial
Habit: Shrub , Vine
Leaf Retention: Deciduous
Leaf Arrangement: Alternate
Leaf Complexity: Trifoliate
Leaf Shape: Obovate , Ovate
Leaf Venation: Pinnate
Leaf Margin: Lobed
Fruit Type: Drupe
Size Notes: Shrub-like, up to about 10 foot tall, or vine-like, up to about 75 feet long.
Leaf: Reddish-green early then green, brilliant red or yellow in fall.
Fruit: Grayish-white.

Bloom Information

Bloom Color: Yellow , Green
Bloom Time: Mar , Apr , May , Jun , Jul
Bloom Notes: Flower inconspicuous.


USA: CA , NV , OR , WA
Canada: BC
Native Distribution: Washington to Baja California, east to Arizona.
Native Habitat: Shady to open woods, streambanks, thickets in damp bottomlands.


Warning: All parts toxic.
Interesting Foliage: yes

National Wetland Indicator Status

Status: FAC
This information is derived from the U.S. Army Corps of Engineers National Wetland Plant List, Version 3.1 (Lichvar, R.W. 2013. The National Wetland Plant List: 2013 wetland ratings. Phytoneuron 2013-49: 1-241). Click here for map of regions.

Web Reference

Webref 62 - Burke Herbarium Image Collection (2020) University of Washington
Webref 30 - Calflora (2018) Calflora
Webref 23 - Southwest Environmental Information Network (2009) SEINet - Arizona Chapter

Additional resources

USDA: Find Toxicodendron diversilobum in USDA Plants
FNA: Find Toxicodendron diversilobum in the Flora of North America (if available)
Google: Search Google for Toxicodendron diversilobum


Record Modified: 2023-05-25
Research By: TWC Staff

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