Romaine lettuce is the most upright growing of all lettuce types. Its heavily ridged leaves grow erectly and tightly to form an elongated head. Its outer leaves, rich in chlorophyll have lime colors while its inner leaves are yellow to creamy. Its blanched heart becomes translucent white at its core. Romaine lettuce has more texture than flavor. Its leaves are substantial, crunchy and succulent with a mild flavor that allows Romaine lettuce to be a very versatile culinary green and multipurpose ingredient in the kitchen.Romaine lettuce is named for the eternal city of Rome, it is originally believed to have been discovered by the Romans on the Aegean Island of Cos. It is documented as being the oldest known cultivated lettuce, having been grown for at least 5,000 years. It is a cool-season crop, as are most lettuce varieties, thriving in rich organic soil and climates with warm days and cool nights. Romaine lettuce is best harvested once the leaves are at least four to six inches in length.