Botanically known as Lactuca Sativa, Romaine Lettuce is believed to be one of the oldest varieties of Lettuce. Romaine lettuce is said to have been in use as early as 55 B.C, being served in spreads for Persian Kings for their culinary and medicinal values. Romaine lettuce is also known as Cos Lettuce. With their elongated shape, Romaine lettuce heads can grow up to 4 to 6 inches long with upright leaves. The outer leaves of romaine lettuce are dark green with noticeably lighter green around the central part. The mild and crunchy taste of this variety of lettuce is perfect for tossed salads, sandwiches if you want that extra crisp. Romaine lettuce can also withstand heat which makes it fit for boiling, braising with other vegetables. On the nutritional profile, this green also ranks higher being an excellent source of vitamins A, C, and K, dietary fibers, potassium, iron, and folate. The leaves of romaine lettuce remain fresh for a week if you keep the moisture in check stored in a refrigerator.