Due to the resurgence in popularity of the Caesar salad, Romaine lettuce has now overtaken the supermarket shelf-space once dominated by crisphead lettuce. The Romaine variety typically consists of thick, crinkled upright leaves with broad juicy stems. The centre of the plant usually develops a small blanched head. North America, Southern Europe, and the Mediterranean share a passion for this culinary treasure. Quick to bolt, this variety is better suited to early spring or autumn sowing. The warmer it gets, the more bitter it will become.