A. The sumac served at Middle Eastern restaurants is a tart spice that adds plenty of flavor to the food, not poison. But the plants you refer to are related to the source of the spice, and they are poisonous.
According to the website, TheSpiceHouse.com, “Sumac is considered essential for cooking in much of the Middle East; it served as the tart, acidic element in cooking prior to the introduction of lemons by the Romans. In the U.S., you might see sumac growing along the roadside, but this relative of the Middle Eastern sumac is poisonous and should not be consumed. Sumac has a very nice, fruity-tart flavor which is not quite as overpowering as lemon. In addition to their very pleasant flavor, flakes from the berry are a lovely, deep red color which makes a very attractive garnish.”
Ground sumac is the form most often seen at Middle Eastern restaurants, including Shiraz, 4230 McCullough Ave.
So, the answer to your question is this: If you want to try this spice at home, buy it from a grocer and don’t pick it from the side of the road.