Large Leaf Sorrel, also called spinach dock and narrow-leaved dock, is a hardy perennial herb in the same family as buckwheat and rhubarb. It produces dome of the earliest greens in the spring! Named after the French translation for "sour," sorrel has an incredibly intense lemony tang. They are excellent in salads and fish. The large leaves grow up to 8 inches tall and can be cooked like spinach or used in soups. Sorrel leaves are also used in Vietnamese cuisine, where they are known as rau thom (fresh herb).