One of the five distinct types of garden lettuce used for salad greens and other dishes. The leaf is similar to romaine lettuce, but unlike romaine, is not considered edible due to the milky sap that forms soon after it matures. Celtuce is grown for the thick stem, approximately 1" to 2" in diameter and 6" to 7" in length. The stem is separated from the leaf, cut into pieces, and used in salads, stews and steamed dishes. Celtuce is also known as asparagus lettuce, celery lettuce, Chinese lettuce or stem lettuce.