This is a crisp head (iceburg type) lettuce. While the leaves are quite delicious, It is the heads most of us want. They head up much like a cabbage. Once I see the head forming I gently squeeze it. When ready it will hard and tight. It needs the leaves to form the head, so unless you are desperate for lettuce just let it do its thing until the heads are ready. I grow Cos and sometimes a leaf lettuce to use before the icebergs are ready.