Lettuce

Lactuca sativa

1. Identification and origin

Lactuca sativa L. is an annual herbaceous species of the Asteraceae family, known as lettuce. It is native to the Mediterranean region and the Middle East, having been domesticated from Lactuca serriola L.. It is currently cultivated worldwide, being one of the most consumed fresh leafy vegetables.

2. Economic importance

Lettuce is one of the most economically important vegetable crops globally, due to its high fresh consumption, the diversity of commercial types and continuous production throughout the year. It is widely used in salads, food service and the fresh-cut (IV gama) industry. The high demand for sanitary quality and appearance makes the crop central to intensive horticulture, both outdoors and in greenhouses.

3. Botanical characterisation

Annual herbaceous plant, low-growing, with leaves arranged in a rosette. The leaves vary in shape, texture and colouring according to the varietal group (batavia, romaine, iceberg, loose-leaf, among others). The flowers are small, yellow, grouped in capitula typical of the Asteraceae. The plant reproduces by seed. The cycle is relatively short, allowing several harvests per year.

4. Soil and climate requirements

It prefers cool climates, with optimal temperatures between 12–20 °C. It is sensitive to excessive heat, which causes premature bolting and bitterness of the leaves. It requires fertile, well-drained soils, rich in organic matter and with a pH between 6.0–7.0. It needs regular and uniform irrigation, avoiding water fluctuations that affect quality and favour physiological disorders.

5. Main pests

• Aphids (Aphididae): deformations and transmission of viral diseases.
• Whitefly: Aleyrodidae causes weakening and sooty mould.
• Thrips: Frankliniella occidentalis causes silvering and cosmetic damage.
• Slugs and snails: perforations in young leaves.
• Nematodes: Meloidogyne spp. can affect root development.

6. Main diseases

• Downy mildew: Bremia lactucae causes chlorotic spots and white sporulation.
• Botrytis: Botrytis cinerea causes rots under humid conditions.
• Sclerotinia: Sclerotinia sclerotiorum and S. minor cause crown rots.
• Powdery mildew: Golovinomyces cichoracearum forms white mycelium on leaves.
• Root rots: Pythium and Rhizoctonia affect seedlings and young plants.

7. General crop management

It includes the use of healthy seedlings, planting in well-drained soils, regular irrigation, weed control and monitoring of pests and diseases. Adequate ventilation in greenhouses reduces the risk of foliar diseases. Crop rotation and structure hygiene are essential to prevent sanitary problems. Harvesting must be carried out at the optimal point of development, avoiding mechanical damage.

Bibliographic references

• EPPO Global Database – Lactuca sativa.
• CABI – Crop Factsheets – Lactuca sativa.
• Rubatzky, V. E., & Yamaguchi, M. (2012). World Vegetables. Springer.
• Kays, S. J. (2011). Cultivated Vegetables of the World. Wageningen Academic Publishers.
• FAO – Technical documents on vegetable production.
• Ryder, E. J. (1999). Lettuce, Endive and Chicory. CABI.