Rhubarb is a perennial plant with large, long stalks ranging in color from greenish pink to dark red. Although a vegetable, rhubarb is eaten as a fruit, cooked and sweetened with sugar. It is also called pieplant because the slender stalks make a delicious pie filling. Discard the leaves and roots, which can be toxic. Select crisp, firm young stalks and store them, wrapped, in the refrigerator, for up to 1 week.