A Springtime patch of Poison Oak in its "green phase" showing the classic three "leaflets" that make up the actual compound leaf. This plant is not an Oak but is in the Sumac family.
It gets its name from its lobed leaflets that resemble the leaves of Old World oak trees. The rash caused by Poison Oak is the result of the skin's reaction to Urushiol Oil, contained in both the leaves and stems of this plant and its close cousin, Poison Ivy (Toxicodendron rydbergii). Click here for view of this plant's appearance from later in the year.

Poison Oak in its "red phase" that occurs in late summer, early fall, again showing the classic three "leaflets" that make up the actual plant leaf.
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