Romaine lettuce (Lactuca sativa) is a type of head lettuce that is typically deep green with elongated leaves. Known for its mild flavor and crisp texture, it has sturdy leaves that make it more tolerant to heat than other lettuce varieties. It is most commonly used as salad greens, although it can also be grilled and sautéed. In recent years, romaine has become a grilling staple along with other vegetables.