Western Poison-oak

Toxicodendron diversilobum Pacific poison oak
Pacific poison oak (larger leaves) at base of an oak tree
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Sapindales
Family:	Anacardiaceae
Genus:	Toxicodendron
Species:	T. diversilobum
Binomial name
Toxicodendron diversilobum (Torr. & A.Gray) Greene
Synonyms
Rhus diversiloba Torr. & A.Gray

Rhus diversiloba Torr. & A.Gray

Toxicodendron diversilobum (syn. Rhus diversiloba), commonly named Pacific poison oak or western poison oak, is a woody vine or shrub in the Anacardiaceae (sumac) family. It is widely distributed in western North America, inhabiting conifer and mixed broadleaf forests, woodlands, grasslands, and chaparral biomes. Like other members of the Toxicodendron genus, T. diversilobum causes itching and allergic rashes in many humans after contact by touch or smoke inhalation.

Toxicodendron diversilobum is found in California (also the original name of Los Angeles; Yangna or Iyaanga/poison oak place), the Baja California Peninsula, Nevada, Oregon, Washington, and British Columbia. The related T. pubescens (eastern poison oak) is native to the Southeastern United States. T. diversilobum and T. rydbergii (western poison ivy) hybridize in the Columbia River Gorge area.

Toxicodendron diversilobum is common in various habitats, from mesic riparian zones to xeric chaparral. It thrives in shady and dappled light through full and direct sunlight conditions, at elevations below 5,000 feet (1,500 m). The vining form can climb up large shrub and tree trunks into their canopies. Sometimes it kills the support plant by smothering or breaking it. The plant often occurs in chaparral and woodlands, coastal sage scrub, grasslands, and oak woodlands; and Douglas-fir (Pseudotsuga menzesii), hemlock–Sitka spruce, Sequoia sempervirens (coast redwood), Pinus ponderosa (Ponderosa pine), and mixed evergreen forests.

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