Rhubarb is a perennial vegetable (yes, vegetable) characterized by long crimson or light green stalks topped by large ruffled green leaves. Although the Chinese have used rhubarb medicinally for thousands of years, its use as a food source is a relatively recent development, particularly after the 17th century when sugar became more widely available and it became a popular addition to pies and other desserts. Today, it's commonly paired with strawberries or other sweet fruits to balance out its tart flavor.