Toxicodendron (Rhus) diversilobum (Pacific Poison Oak)

Photographs

My photos:

This photo was taken in January in Caspers Wilderness Park in February. Some of the stems are bare of leaves.

The photo below was taken at Mt Palomar in April, with the new leaves starting to grow.

There was lots of Poison Oak at Holy Jim Canyon.

More photos:

Coe shows closeup of leaves in spring and in autumn, bushy and of vining plants, and fruit.

Montara shows the flowers and has some interesting information on the Anarcadia family.

click photo to enlarge

Plant Information

Anacardiaceae

In the garden:

Toxicodendron means ‘poison tree,’ and as the name implies, this plant is a hazard to most people. It is very oily and exposure to this oil may result in a painful dermatitis. Even breathing the smoke from burning plants is harmful. It is wise to wash thoroughly after any possible exposure, especially before ingesting food. This is not a plant that should be tolerated in the garden.

This plant is hardest to identify during winter and early spring because it consists of bare branches - even these branches may cause the typical rash if brushed against. It produces suckers, especially if it’s roots are disturbed by soil cultivation. It does require some water.

The best method for eradicating is by using a chemical brush killer.

In the wild:

Poison Oak is usually an erect, bushy shrub, 3 to 6 feet tall. It is stiffly branched and deciduous. Leaves are pinnately 3-foliate, bright green, and shiny above (somewhat paler beneath). In the fall, the foliage will turn a bright orange or scarlet. It is common in low places, thickets, and wooded slopes, below 5000 feet. In the open or in filtered sunlight, it will grow as a dense leafy shrub. Where shaded, it becomes a tall-climbing vine. It is hardy anywhere and will thrive in poor soils.

Ethnobotany:

Not surprisingly, the local native people had remedies for the dermatitis caused by Poison Oak. Some used an infusion of the leaves of Arctostaphylos glauca, A. glandulosa or A. pungens for the rash. Others used Ceanothus leucodermis together with cascara (Rhamnus californica? R. ilicifolia? R. crocea?) leaves, Grindelia camporum, or G. hirsutula for the same purpose. Severe cases were treated with a decoction of Salvia apiana leaves.

Poison Oak has its own medicinal value. A decoction of the roots was used for eye ailments. And it seems that some brave souls used the shoots in basketry, and the leaves to wrap baking loaves of bread.

Field Trips
Anza Borrego Caspers Holy Jim Canyon Idyllwild
Joshua Tree Mt Palomar Rancho Santa Ana Torrey Pines

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