Close up of poison oak leaves.  Copyright © 2005 by Lawrence M. Kelly


Poison Oak

Toxicodendron diversilobum or common name "Western or Pacific Poison Oak" is part of the Toxicodendron genus meaning poison tree.  The poison oak gets its common name from its leaves looking similar to those of the oak trees.  The leaves of the poison oak have three lobes very similar to its fellow member in the Toxicodendron genus poison ivy.  Therefore the rule for poison ivy, "leaves of three let them be" also applies to the poison oak.  Poison oak can appear as a vine or a shrub and can be a hikers worst enemy.  This plant is the number one shrub in California alone and it is spread all along the Pacific Coast.  If you ever come into contact with this plant be very careful as you may be susceptible to its poison, urushiol, causing an itchy and sometimes painful rash.  Explore this website to learn all you can about this annoying yet amazing plant!  Visit for even more great student web pages!

Sign warning against the dangers of touching poison oak.

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