There are five general types or classifications of lettuce: Butterhead, Crisphead, Looseleaf, Romaine, and Celtuce.
Butterhead and Crisphead types have crisp leaves that form compact hearts.
Looseleaf and Romaine types grow best in cool weather and do not form significant hearts.
Celtuce is a cross between celery and lettuce and is valued for its stem.
Butterhead is a smooth, sweet-tasting lettuce with a delicate, buttery texture.
Butterhead varieties—which are sometimes called cabbage lettuce–form a small, loose, slightly flattened head that look something like an open rose.
Butterhead—which is also commonly called by its variety names such as Bibb, Boston, and Limestone—has broad, crumpled, succulent, pale-green outer leaves and yellow to cream colored leaves at the center.
Butterheads form heads as large as 7 inches (18 cm) or more in diameter. They are much easier to grow than crisphead lettuce—the other main type of heading lettuce.
Batavia-type butternead cultivars have features between crisphead and butterhead plants.
The best-known varieties of butterhead lettuce are: ‘Buttercrunch’ is very tender; ‘Boston’ forms a medium-large head of loosely arranged broad light-green leaves; ‘Bibb’ has a smaller more compact head of short dark-green leaves edged with dark-red; ‘Limestone’ which is very similar to Bibb but is named for the limestone soil in Kentucky and Indiana where it grows best; and ‘Four Seasons’ (‘Merveille Des Quatres Saisons’) has red outer leaves and pink and cream inner leaves.
The botanical name for butterhead lettuce is Lactuca sativa var. capitata.
Crisphead lettuce has a solid spherical head of tightly-wrapped, pale green leaves that are crisp and succulent. Crispheads have a neutral, watery flavor.
Crisphead lettuce is most commonly known as head lettuce or iceberg lettuce. The name iceberg was given to crisphead in the 1920s when California lettuce growers began shipping lettuce to far off markets in rail cars chilled with crushed ice.
Crisphead lettuce has outer leaves that are dark green and inner leaves that are greenish white to white. Because crispheads consist of layers of tightly packed leaves, they are more tolerant of heat and keep longer than leaf lettuces.
Varieties of crisphead include: ‘Great Lakes’, the classic iceberg-type lettuce, ‘Ithaca’, which is glossy-green, frilled-leaf improved iceberg, and ‘Imperial’ with dark green heads.
Batavian lettuce is a French type of crisphead that opens like a looseleaf lettuce but later develops a dense head at maturity. It is sweet and juicy without bitterness.
The botanical name of crisphead lettuce is Lactuca sativa var. capitata.
Looseleaf lettuces form tight rosettes of individual leaves that are crisp and buttery-flavored. Looseleaf do not form hearts or heads.
There are many variations in the leaf size, leaf margins, color, and texture of looseleaf lettuces. Some leaves can be smooth, some curled, some ruffled, some crinkled, and some oak-leaf shaped. Looseleafs can be yellow, green, red, reddish-bronze, or purplish in color.
Looseleaf varieties are often named for how they look: ‘green leaf’, ‘red leaf’,’ oak leaf’.
‘Green Ice’ is light green and crispy. ‘Red Sails’ has crinkly leaves edged with bright red.
‘Black-Seeded Simpson’ has extra-large frilled leaves. ‘Red Sails’ has heavy, ruffled leaves that are deep red-bronze colored. ‘Lollo Rosa’ has frilly magenta leaves with light green edges. ‘Salad Bowl’ has wavy, light-green, deeply lobed leaves.
The botanical name for looseleaf lettuce is Lactuca sativa var. crispa.
Romaine lettuce has a large, upright, loaf-shaped head with long narrow stiff leaves that look coarse but are crisp, tender, and sweet.
Romaine lettuce outer leaves are dark green and 8-9 inches (20-23 cm) long with a distinctive rib that reaches to the tip. The inner leaves are greenish-yellow surrounding a succulent heart.
Romaine lettuce has been cultivated for more than 5,000 years. It is sometimes called Cos lettuce—named for the Greek island of Kos (Cos) off the coast of Turkey where it is believe to have originated.
Romaine varieties are very popular in the United States, southern Europe, and Mediterranean countries. Romaine lettuce was given its name by the ancient Romans and is the chief ingredient of Caesar salad.
Common varieties of Romaine lettuce are ‘Rouge D’Hiver’ with bronze to deep red, broad, flat leaves, ‘Jericho’ with sword-shaped leaves, and ‘Paris White Cos’.
Romaine lettuce is usually planted for a fall crop because it does not produce heads during warm weather. In the late summer, Romaine leaves can be tied together to form elongated heads.
The botanical name of Romaine lettuce is Lactuca sativa var. longifolia.
Celtuce–also known as stem lettuce–is grown for its succulent, thick stem and tender leaves.
The name celtuce is a combination of “celery” and “lettuce.” The flavor of celtuce is similar to celery or cucumber or zucchini or artichoke or a combination of the four.
The stem of celtuce can be pared to remove its bitter skin leaving the soft translucent green core that can be finely sliced and eaten raw in a salad. Celtuce can also be sliced or shredded and stir-fried with other vegetables, pork, chicken, or prawns.
The stem of celtuce can grow about 10 to 12 inches (25-30 cm) long. There are soft green lettuce-like leaves at the end.
The young leaves of celtuce can be eaten raw in salads, but the leaves become tough, bitter, and inedible as they mature.
Celtuce—which is sometimes called asparagus lettuce for its stalk’s resemblance to an asparagus spear– is thought to have originated in China. Celtuce grown in China is sometimes pickled and eaten as a side dish.
The botanical name of celtuce is Lactuca sativa var. angustana.
Tips on growing lettuce at How to Grow Lettuce.