romaine

Romaine lettuce, or cos lettuce, is a cultivar of Lactuca sativa L. var. longifolia. It forms elongated heads with crisp, pale green to dark green leaves and a distinct, sturdy central rib. The leaf margins are smooth, and the outer leaves are more loosely arranged than the tightly packed inner leaves. Romaine is sold in green varieties and, less commonly, red-tinged forms. The name romaine derives from French, while cos refers to the Greek island of Kos, historically associated with the lettuce’s origin.

Used widely in salads and sandwiches, romaine is the traditional leaf used in Caesar salad. It can also be grilled or braised briefly in some cuisines. It is grown commercially in temperate climates and in greenhouses; it prefers cool growing conditions, full sun, and well-drained soil rich in organic matter. It requires regular moisture and steady temperatures to form a tight head; hot weather can cause bolting and bitterness. Days to maturity vary by cultivar but generally range from about 65 to 85 days.

Nutritionally, romaine provides relatively few calories and is a good source of vitamins A and K, folate, and minerals such as potassium. It is typically considered a healthy addition to salads and wraps. In recent years, romaine lettuce safety has been a concern due to outbreaks of pathogenic bacteria; producers and retailers emphasize careful handling, washing, and proper refrigeration to reduce risk.