Jepson (2012) (APG System)





Jepson (1993) (Cronquist System)



These plants were formerly classified in the genus Rhus (sumac). Those species that produced the rash causing chemical urushiol were separated into the genus Toxicodendron.


California Native Plant Guide
Native Plant Genera

Plant Relationships

California Species:

Toxicodendron diversilobum

Poison oak

Other Species:

Toxicodendron radicans
Toxicodendron vernix

Poison ivy
Poison sumac


Growth Forms:

Toxicodendron diversiloba grows as a clambering shrub, with many semi-erect, thin branches. Rarely, it grows as a vine. By contrast, T. radicans is a vine that fixes tightly to the sides of trees. It rarely is found as a clambering shrub. T. vernix is a shrub.


Alternate branching in a spiral pattern around the stem.


Toxicodendron diversiloba and T. radicans are pinnately compound with three leaflets. T. vernix is pinnately compound with 7 - 13 leaflets per leaf. All are deciduous.


Flowers are in panicles or racemes. They tend to stand upward at the ends of branches.


Fruits are drupes with a white or off-white color.

Growing Conditions

Sun and Exposure:

They prefer full sun, but will tolerate minor shade. T. diversiloba is often found in sunny, but not harsh locations, such as full sun on a north or east facing slope.

Soil and Moisture Requirements:

Toxicodendron is found primarily on well structured, deep forest soils. They prefer, but are not limited to, sites with easily available summer moisture. T. vernix is found in moist sites and bogs in the eastern United States.

Natural Habitat and Range:

These are woodland species, and are usually found in clearings in the forest or on the borders of grasslands. T. diversiloba is very adaptable, however, and is found in a wide variety of habitats. For example, it is common as a low growing, almost invisible plant in coastal prairies on seabluffs.

Horticulture and Restoration

Horticultural Comments:

These are vigorous, fast growing plants. They are some of the most successful plants in the native flora. We have not experimented with them, but they have all the indicators of an easily propagated and outplanted species. If not for the rashes they cause, these would be highly popular native plants.

Wildlife Habitat:

Fruit are eaten by wildlife. Although many animals, notably humans, are allergic to the urushiol these plants produce, many species are unaffected, and eat the fruit and foliage.

Restoration Projects:

Toxicodendron is not used in restoration, for the obvious reasons. It would otherwise be very useful and successful in restoration and landscaping.

California Native
Plant Guide

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