Lettuce
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Vegetables
Lettuce
Latin:
Lactuca scariola
Origin:
Lettuce, a cultivated annual salad plant, is probably derived from the prickly lettuce Lactuca scariola var. integrata (B,P) L., or Lactuca sativa L., of the family Compositae.
, http://www.100md.com The annual plant grows to about 0.8 m by 0.25 m. It is in flower from July to August, and the seeds ripen from August to September. The flowers are hermaphrodite (have both male and female organs) and are pollinated by flies. The plant is self-fertile. It can grow in semi-shade (light woodland) or no shade, and requires moist soil.
Lettuce is widely cultivated in many parts of the world for its edible leaves and is probably the most commonly grown salad plant. There are many named varieties capable of providing fresh leaves throughout the year if winter protection is given in temperate areas.
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There are two classes of head lettuce: the butter-head types with soft heads of thick, oily leaves, and crisp-head types with brittle-textured leaves that form very hard heads under proper temperature conditions.
For successful cultivation lettuce requires ample water, especially in warmer weather. During unseasonable weather, protection is furnished and growth stimulated with greenhouses, frames, cloches, or polyethylene covers.
, http://www.100md.com In many parts of the world the leaf and butter-head types are most popular. They are not suitable for shipping, so they are usually grown on truck farms or market gardens relatively close to markets.
The crisp-head varieties, well adapted for long-distance shipment, are dominant in the U.S., where over five-sixths of the acreage is located in California and Arizona.
Lettuces are quite a problematic crop to grow. They require quite a lot of attention to protect them from pests such as slugs, aphids and birds. If the weather is hot and dry the plants tend to run very quickly to seed, developing a bitter flavor as they do so. In wet weather they are likely to develop fungal diseases. In addition, the seed needs to be sown at regular intervals of 2-3 weeks during the growing season in order to provide a regular supply of leaves.
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Lettuces make a good companion plant for strawberries, carrots, radishes and onions. They also grow well with cucumbers, cabbages and beetroot.
Lettuce is available all year long and is at its peak from mid-winter to early spring.
Also called Garden Lettuce.
Properties:
Sweet and bitter in flavor, cool in nature, it is related to the stomach and large intestine channels.
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Functions:
Promotes urination and milk secretion; rejuvenates the respiratory track and is a nervine tonic.
Applications:
Lettuce is used to dimish urination, to treat blood in urine and shortage of milk secretion in nursing mother.
Dosage and Administration:
As a food, although lettuce is most commonly consumed in salads, it may also be served as a cooked vegetable.
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The leaves are consumed raw or cooked. A mild slightly sweet flavor 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.
Wash lettuce just before using and drain or blot with paper towel to remove any excess moisture, or dry in a salad spinner. Toss with other salad greens, or stuff individual leaves with hummus and them roll up for a light lunch.
The sprouted seeds are used in salads or sandwiches.
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An edible oil is obtained from the seed. The seed is very small, extraction of the oil on any scale would not be very feasible.
Lettuce can be found in the produce section of most health food stores and supermarkets. Choose heads with crisp, blemish-free leaves and no signs of browning or wilting. Wrap lettuce in a paper towel refrigerate it in a plastic bag for up to three days.
Cautions on Use:
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The mature plant is mildly toxic.
When used as a medicine, 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 and overdoses can cause death through cardiac paralysis.
Reference Materials:
Toxic or Side Effects:
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Modern Researches:
Lettuce leaves contain water, protein, carbohydrate, fibre, ash, calcium, phosphorus, iron, magnesium, sodium, potassium, vitamins A, C, niacin, etc.
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. The sap contains "lactucarium", which is used in medicine for its anodyne (relieves pain), antispasmodic, digestive, diuretic, hypnotic, narcotic and sedative properties. Lactucarium has the effects of a feeble opium, but without its tendency to cause digestive upsets, nor is it addictive.
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Lactucarium is taken internally in the treatment of insomnia, anxiety, neuroses, hyperactivity in children, dry coughs, whooping cough, rheumatic pain, etc. Concentrations of lactucarium are low in young lettuce plants and most concentrated when the plant comes into flower.
Lactucarium 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. The cultivated lettuce does not contain as much lactucarium as the wild species, most being produced when the plant is in flower. An infusion of the fresh or dried flowering plant can also be used.
The sap has also been applied externally in the treatment of warts.
The seed is anodyne (serving to assuage pain) and galactogogue. It is also said to be used to make hair grow on scar tissue., 百拇医药