Iceberg lettuce, green leaf lettuce, red leaf lettuce, romaine lettuce and Boston lettuce are commonly sold in grocery stores. Little gem lettuce, oak leaf lettuce and celtuce are less common.
Crisphead and butterhead varieties, which, respectively, include iceberg and Boston lettuce, form compact heads and have distinct hearts at the centers of the heads. Looseleaf varieties, including green leaf lettuce, do not have compact cores and have leaves that are arranged more loosely around the stem. Romaine lettuce, which has its own category, is long with tightly arranged leaves. Celtuce has a thick stem and is a cross between celery and lettuce.