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PlantFiles: Western Poison Oak, Pacific Poison Oak
Toxicodendron diversilobum

Family: Anacardiaceae (an-a-kard-ee-AY-see-ee) (Info)
Genus: Toxicodendron (toks-ee-ko-DEN-dron) (Info)
Species: diversilobum (die-ver-sih-LOW-bum) (Info)

Synonym:Rhus diversiloba
Synonym:Toxicodendron radicans subsp. diversilobum


36-48 in. (90-120 cm)
4-6 ft. (1.2-1.8 m)
6-8 ft. (1.8-2.4 m)

Unknown - Tell us

USDA Zone 5a: to -28.8 C (-20 F)
USDA Zone 5b: to -26.1 C (-15 F)
USDA Zone 6a: to -23.3 C (-10 F)
USDA Zone 6b: to -20.5 C (-5 F)
USDA Zone 7a: to -17.7 C (0 F)
USDA Zone 7b: to -14.9 C (5 F)
USDA Zone 8a: to -12.2 C (10 F)
USDA Zone 8b: to -9.4 C (15 F)
USDA Zone 9a: to -6.6 C (20 F)
USDA Zone 9b: to -3.8 C (25 F)

Sun Exposure:
Unknown - Tell us

All parts of plant are poisonous if ingested
Handling plant may cause skin irritation or allergic reaction

Bloom Color:
Unknown - Tell us

Bloom Time:
Unknown - Tell us

Good Fall Color

Other details:
May be a noxious weed or invasive

Soil pH requirements:
Unknown - Tell us

Patent Information:

Propagation Methods:
Unknown - Tell us

Seed Collecting:
Unknown - Tell us

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1 positive
No neutrals
1 negative

Gardeners' Notes:

Negative palmbob On Feb 1, 2011, palmbob from Acton, CA (Zone 8b) wrote:

I am surprised there are not more comments about this plant. From a personal experience perspective, this is a species that would keep me from living in certain geographical areas of California thanks to is prevalence in those areas. It is an innocuous looking plant that is somewhat identifiable when in leaf, but very hard to pick out in its leafless form (a good 1/3 of the year in most areas), yet still as dangerous.

The saps from this plant are not toxic to everyone, but abouit 80% of the people who contact it develop an allergic reaction to it. I am included in that 80% though reportedly me father was in the lucky 20% that are not (I never got to test it on him to see if that was true, though).

Having not grown up in northern California where this plant is ubiquitous, I was not aware of its appearance or presence everywhere. After one visit to the countryside near Napa I began to itch uncontrollably and, to my dismay, discovered I had obviously been handling this plant or touching it somehow as I had gotten it nearly everywhere on my body (if you get the oils on your hands, you then can transfer the oils to any area you then touch with your hands... you would be amazed how many areas you touch with your hands!). The next day I was in the hospital as my eyes had swollen shut and my face was a mass of swollen, oozing pustules that burned like mad (the 'itching phase' had long ceased by this point and now I was just in pain). They gave me a long acting cortisone injection and in 24 hours I could easily see again and was nearly cured in a week.

Since then I have had multiple milder exposures to this plant, once from a dog that had been running through some obviously. I avoid the heavily forested areas of northern California where this plant grows now. Thank goodness it is far more uncommon in southern California where I hike frequently (it's here, but not 'everywhere' as it is in some areas of northern California).

People complain about Euphorbia saps, but I have been exposed to Euphorbia saps hundreds and hundreds of times and nothing comes close to my experience with this plant. Thankfully, it is not an interesting ornamental and not one I would be tempted to grow for that reason, as I have a long list of toxic dangerous plants in my collection.

Positive Happenstance On Apr 15, 2005, Happenstance from Northern California, CA wrote:

Actually a very nice looking shrub with glossy green foliage in spring and red hues in the fall. Growing at the bottom of our downhill slope, I've left it alone and stay at a distance!


This plant has been said to grow in the following regions:

Castro Valley, California
Fortuna, California
Fremont, California
Malibu, California
River Pines, California
San Mateo, California
San Antonio, Texas
Seattle, Washington

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