Lettuce, Garden lettuce

Lactuca sativa

Physical Characteristics

Lactuca sativa is a ANNUAL/BIENNIAL growing to 0.9 m (3ft) by 0.3 m (1ft in). See above for USDA hardiness. It is hardy to UK zone 6 and is not frost tender. It is in flower from July to August, and the seeds ripen from August to September. The species is hermaphrodite (has both male and female organs) and is pollinated by Flies. The plant is self-fertile. Suitable for: light (sandy) and medium (loamy) soils and prefers well-drained soil. Suitable pH: neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil.

Distribution

Of garden origin, probably derived from L. serriola.

Habitats

Cultivated Beds;

Edible Uses

Edible Parts: Leaves Oil Seed Edible Uses: Oil Leaves - raw or cooked[7, 37]. A mild slightly sweet flavour with a crisp texture, lettuce is a very commonly used salad leaf and can also be cooked as a potherb or be added to soups etc[183]. A nutritional analysis is available[218]. Seed - sprouted and used in salads or sandwiches[183]. An edible oil is obtained from the seed[7]. The seed is very small, extraction of the oil on any scale would not be very feasible[K].

Medicinal Uses

Anaphrodisiac Anodyne Antispasmodic Carminative Diuretic Emollient Expectorant Febrifuge Galactogogue Hypnotic Hypoglycaemic Narcotic Parasiticide Parasiticide Sedative The whole plant is rich in a milky sap that flows freely from any wounds. This hardens and dries when in contact with the air[4]. The sap contains 'lactucarium', which is used in medicine for its anodyne, antispasmodic, digestive, diuretic, hypnotic, narcotic and sedative properties[9, 21, 46, 165, 192, 213, 238]. Lactucarium has the effects of a feeble opium, but without its tendency to cause digestive upsets[4], nor is it addictive[7]. It is taken internally in the treatment of insomnia, anxiety, neuroses, hyperactivity in children, dry coughs, whooping cough, rheumatic pain etc[238]. Concentrations of lactucarium are low in young plants and most concentrated when the plant comes into flower[238]. It is collected commercially by cutting the heads of the plants and scraping the juice into china vessels several times a day until the plant is exhausted[4]. The cultivated lettuce does not contain as much lactucarium as the wild species, most being produced when the plant is in flower[4]. An infusion of the fresh or dried flowering plant can also be used[9]. The plant should be used with caution, and never without the supervision of a skilled practitioner. Even normal doses can cause drowsiness whilst excess causes restlessness[238] and overdoses can cause death through cardiac paralysis[7, 9]. Some physicians believe that any effects of this medicine are caused by the mind of the patient rather than by the medicine[213]. The sap has also been applied externally in the treatment of warts[222]. The seed is anodyne and galactogogue[218]. Lettuce has acquired a folk reputation as an anaphrodisiac, anodyne, carminative, diuretic, emollient, febrifuge, hypoglycaemic, hypnotic, narcotic, parasiticide and sedative[218].

Known Hazards

The mature plant is mildly toxic[13].