Both Poison Oak and Poison Ivy have seed in drupes, which are eaten by mammals and birds. The seed aren't digested and are subsequently ejected, with a small measure of Nitrogen fertilizer! This insures that almost every seed will germinate, wherever it makes contact with the soil.

Just to be sure that you have Poison Oak, check the link below for photos of Poison Ivy, Poison Oak, Poison Sumac and look-alike plants.
Poison Ivy is more common and can form a shrub like plant, if no plant or structure is available for attaching it's tendrils.
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Here is a link that might be useful: Poison Ivy/Oak/Sumac

Thank you and I will get a picture of it to show you what it looks like. I planted Devil Claws seeds there.