Rhubarb stalks are used in the spring as a fruit substitute to make pies and preserves. They are pleasantly acidic from the oxalic acid which they contain. The stalks must be peeled before they are sliced for use. Rhubarb (genus Rheum of the buckwheat family) obtained its name from ancient Greeks who called it "the vegetable of barbarians beyond the Rha (Volga) River." The leaves of the Rhubarb plant are not edible. Rhubarb gained a bad reputation in World War I when Americans were advised to eat its leaves as a vegetable supplement. Many people were poisoned.