Rhubarb juice is made from the stalks of rhubarb (Rheum rhabarbarum), an herbaceous, perennial plant with thick, fleshy stalks native to China and the area around the Volga river. Though a vegetable, rhubarb is commonly used in pies and baking applications in the United States, as its tartness provides balance to sweeter fruit such as apples or strawberries.
Rhubarb stalks can be either juiced or simmered in a scant amount of water, then pureed and strained to make juice. Raw rhubarb juice is sharper and more acidic than juice made by the simmering method. Rhubarb leaves are toxic and should not be used for any application.