One of two varieties of head lettuce (the other being crisphead). Butterhead lettuces have small, round, loosely formed heads with soft, buttery-textured leaves ranging from pale green on the outer leaves to pale yellow-green on the inner leaves. The flavor is sweet and succulent. Because the leaves are quite tender, they require gentle washing and handling. Boston and Bibb (also called limestone) lettuce are the two most well known of the butterhead family. The smaller Bibb is highly prized by gourmets. Both Boston and Bibb lettuce are sometimes referred to simply as "butterhead" or "butter" lettuce. See also lettuce.