lettuce

Annual plant whose large edible leaves are commonly used in salads. There are many varieties, including the cabbage lettuce, with round or loose heads, the Cos lettuce, with long, upright heads, and the Iceberg lettuce, with tight heads of crisp leaves. They are all believed to have been derived from the wild species L. serriola. (Genus Lactuca, especially L. sativa, family Compositae.)

Iceberg and Romaine are the two salad varieties grown especially for US supermarkets, but Boston and Redleaf are sometimes shipped to markets.