lettuces

Lettuce refers to several leafy greens in the genus Lactuca, most often Lactuca sativa, grown for edible leaves. It belongs to the daisy family, Asteraceae. Major cultivated groups include loose-leaf, butterhead, romaine (cos), and crisphead (iceberg). Loose-leaf varieties have open, savoy-like leaves; butterheads form soft, rounded heads; romaine produces tall, elongated heads with a central rib; crispheads are compact and pale.

Lettuce is a cool-season crop, typically grown in spring and fall in temperate regions. It requires well-drained soil, regular moisture, and protection from bolting in hot weather. Seed is sown directly or transplants are used in some systems. Harvest methods vary by type: cut-and-come-again for loose-leaf, or single-head harvest for butterhead, romaine, and crisphead.

Nutritionally, lettuce is low in calories and high in water content. It provides modest amounts of vitamins A and K, folate, and iron, with darker-green or red cultivars offering more beta-carotene and antioxidants. Water and energy content can vary with variety and preparation.

In culinary use, lettuce is most commonly eaten raw in salads but also used in sandwiches, wraps, and as a garnish. It is generally sensitive to heat, which can cause bolting or bitterness in some varieties.

Pests and diseases, including aphids, slugs, leaf spot, and downy mildew, can affect yields and quality. Proper spacing, crop rotation, and resistant varieties help manage problems.

Lettuce has a long history of domestication from wild Lactuca serriola in the Mediterranean region, with breeding leading to the diverse forms available today. It is grown worldwide in temperate and some subtropical areas, with major production in North America, Europe, and parts of Asia.