Lettuce (Lactuca sativa)

Lettuce (scientific name: Lactuca sativa) is an annual plant belonging to the Asteraceae family, commonly grown as food. It is usually eaten raw and added to salads. It is among the most widely consumed leafy vegetables in the world.

The plant has leaves arranged in whorls that grow from a short stem. When temperatures rise or daylight lengthens, the plant begins to flower and produce seeds—a process called bolting—which makes the leaves tough and bitter. For this reason, growers typically choose cooler seasons.

Varieties

Several major groups exist: the compact 'iceberg' type with densely packed leaves; the 'romaine' or 'cos' type with elongated upright leaves; the soft butterhead type; and loose-leaf types that do not form a head. Leaf color varies, and some varieties have reddish-tinged leaves.

Cultivation

Lettuce requires rich, well-drained soil and regular water. Seeds germinate best at moderate temperatures; high heat inhibits germination. The time from sowing to harvest is usually only a few weeks, making it a fast-growing crop. It is also grown in hydroponic systems and controlled-environment greenhouses.

Use and nutrition

Leaves are eaten in salads, sandwiches, and as raw wraps; some varieties are cooked or fried. Lettuce consists mainly of water, contains little energy, and provides significant vitamins A and K, though nutrient levels vary by variety—darker-coloured leaves generally contain more nutrients.

Food safety

Because it is usually eaten raw, lettuce can transmit bacteria if irrigation water or handling hands are contaminated. For this reason, washing and sanitizing are recommended. Many countries have issued regulations concerning the cleanliness of leafy vegetable production.