Sumac is tangy and astringent. It is easy to find in Texas along the roadside. Berries grow on small trees here, but are more commonly found growing in shrubs. I don't know what the poison sumac looks like, so I don't bother with it at all. Commonly used in Turkish and Greek dishes.
North American indigenous peoples (Indians) used two native species of sumac - Rhus glabra and Rhis aromatica - to prepare a concoction similar to beer. http://greekfood.about.com/od/greekspices/p/sumac.htm