Watercress (Nasturtium officinale) is a fast-growing semi-aquatic perennial in the cabbage and mustard family, eaten for its small, glossy, dark-green rounded leaflets and crisp hollow stems and prized for a clean, sharp, peppery-mustardy bite. Grown for thousands of years in cool flowing spring water, it is one of the oldest cultivated leafy vegetables and one of the most nutrient-dense of all foods — heaped raw into salads and the British watercress sandwich, blended into the classic French and English potage of watercress soup, or strewn as a peppery bed under roast game and fish.