Lettuce Types

Crisphead--Makes a frilly, loose head with crisp midribs and hearts. Not the same as the round, tight iceberg types (which need a cool climate). The most heat-resistant lettuce, with excellent cold-hardiness as well.
Romaine--Tall heads with juicy midribs and crisp heart. Adaptable, nutrient-dense, and popular.
Butterhead--Soft leaves with a buttery texture and flavor make small round, roselike heads. Most do best in cool weather.
Leaf Lettuce--Open heads are fast-growing and nutritious, because  all the leaves get sunlight. Well-adapted to cutting a few leaves at a time. Hardy and disease-resistant.