Romaine lettuce is a head-forming lettuce. It has deep green and long leaves with a crisp texture and distinct taste. It’s one of four popular lettuce varieties, alongside crisphead, butterhead and leaf lettuce. Just like most lettuce, once romaine lettuce leaves are broken, a white and milky liquid is excreted that’s responsible for its slightly bitter flavor.
Romaine lettuce is also called Cos, because it was said to have originated from the Greek island of the same name located off the coast of Turkey in the Aegean sea.4 In the U.S., California is considered to be the country’s “Lettuce Capital,” since Spanish missionaries planted lettuce in the state as early as the 17th century.