Synonym are Cichorium endivia var. crispa L., Cichorium endivia L.

Common names are Lettuce (Eng.); Laitue (Fr.); Lechuga (Sp.); Salat (Ger.); Sia (Neth.); Letsugas (Philip.).

Botanical varieties are var. asparagina Bailey, syn. L. angustana Vilm., L. sativa L. var. angustana Irish ex Bremer (Asparagus or Stem Lettuce, Celtuce) Mature leaves coarse and inedible; basal leaves narrow, lanceolate, alternate, sometimes with pointed apex, non-heading; young, thickened stems up to 1 m and young leaves used as a cooked vegetable; mainly grown in China, from where it originated. var. capitata L. ( Cabbage, Butterhead or Head Lettuce ) Compact rosettes of leaves forming a solid head; leaves broad, almost orbicular, midrib branching into small veins. var. crispa L. (Leaf Lettuce, Curled Lettuce) - Leaves in loose rosettes, similar to cabbage lettuce but non-heading; some cultivars with curled or crinkled leaves. var. longifolia Lam., syn. L. romana Gars. (Cos or Romaine Lettuce) Rosettes of leaves cylindrical, upright leaves obovate to oblong, coarse in texture; midrib prominent, terminating near rounded leaf apex; leaves mainly self-folding, forming loose heads.

The Middle East, later spreading to Egypt by 4500 BC, Greece and many parts of the Mediterranean before being introduced to China by the seventh century AD. A recent introduction to the tropics. Possibly derived from L. serriola L. which is indigenous to western Asia.

Cultivated to a limited extent in the Caribbean, Malaysia, East and West Africa, mainly at high altitudes.

An annual glabrous herb. Roots: main taproot, with fibrous lateral branches. Stems: cylindrical, containing latex vessels, up to 10 cm in most cultivars but extended to 1 m in L. sativa var. asparagina. Leaves: almost sessile, arranged spirally in rosettes, variable in size and form, 10-25 cm in length. Flowers: pentamerous, yellow, in dense clusters, ligulate and hermaphrodite. anthers connate; stigma bifid. Seeds: achenes, oval, 34 mm in length, ribbed, hairy at one end, white, yellow, grey or brown, pappus of silky hairs; approximately 100 seeds/g.

The crop is tolerant of a wide range of soil conditions but well drained soils with a satisfactory organic content and adequate mineral reserves are most suitable. Reduced yields are obtained from crops grown on heavy clay soils. High temperatures, above 27C, are likely to induce low yields. The water requirements of the crop are not high, but rainfall levels of more than 1500 mm per year are likely to reduce growth and possibly cause rotting of the tubers. Tuber yield is reduced when crops are grown at low elevations and altitudes of more than 500 m are generally required for the production of satisfactory yields. Crops are grown in India at elevations up to 3600 m. Short days appear to promote tuber initiation and development; some forms may show tuber dormancy for periods of up to 150 days.

Seeds are sown in seed beds or containers and transplanted when 5-7 cm in height to rows 30-36 cm apart, 20-25 cm between plants, depending on the vigor of the cultivar. Approximately 0.5 kg of seed is required to plant one hectare. Blanching, which reduces the bitter flavor of the leaves, is induced by tying the leaves together when the plants are approaching maturity, for a period of 1044 days. During wet weather, the internal leaves are liable to rot and decay and this practice is only feasible during relatively dry periods. Irrigation: The requirement for water is moderately high, plants grown during the dry season will require supplementary irrigation. Nutrient requirements: Plants respond well to high levels of organic material in the soil but additional nitrogenous dressings are generally beneficial during the early period of growth.

Plants normally mature within 70-85 days from transplanting, depending on factors such as soil fertility and irrigation efficiency. Yield: Yields in the region of 6-12 t/ha may be obtained. Seed production: Seed is rarely formed in the tropics, except at elevations above 1500 m. Most cultivars are almost completely self-pollinated. A 600 m isolation distance is sufficient unless hybrid seed is being produced, when 1000 m is more appropriate. The average seed yield is 200 kg/ha.

Once they have been harvested, the tubers rapidly shrink and deteriorate if kept at ambient temperatures, but if they are sound and disease-free, they may be successfully stored for periods from 90 to 150 days at 0C in a relative humidity of 90-95% although a significant loss, due to decay and shriveling of tubers, may occur.

he young leaves, preferably blanched, are eaten in salads. The mature green leaves are sometimes used as a cooked vegetable.