While you may have wild sumac growing in your backyard, and you know it's poisonous, there are non-poisonous varieties of sumac that grow in the Middle East that are crushed up in powder and used as a spice.
Sumac spice is commonly found in Middle Eastern cuisine. The dark reddish powder has a zingy, lemony taste and is excellent when sprinkled on chicken, grilled lamb, and hummus. It's also used as an ingredient in zataar, a Middle Eastern spice mix. The spice was long used to add tartness to many dishes until the Romans introduced lemons to the area.
(Image: The Spice Trader)