Rhubarb, the vegetable so celebrated for its role in pastries that it's also known as the "pie plant," has a kick to it. While rhubarb has a medicinal history originating in Asia, ingesting a large amount of the leaves can cause poisoning. The CDC warns that neither cooked nor raw rhubarb leaves should be consumed, owing to the toxins (including oxalate) they contain. Stick with the stalk.