Lettuce

Taxobox
name = Lettuce

---

image_width = 260 px
image_caption = Iceberg lettuce field in Northern Santa Barbara County
regnum = Plantae
divisio = Magnoliophyta
classis = Magnoliopsida
ordo = Asterales
familia = Asteraceae
genus = "Lactuca"
species = "L. sativa"
binomial = "Lactuca sativa"
binomial_authority = L.nutritionalvalue | name=Lettuce (butterhead) | water=96 g | kJ=55 | protein=1.4 g | fat=0.2 g | carbs=2.2 g | fibre=1.1 g | iron_mg=1.2 | vitC_mg=4 | vitA_ug=166 | folate_ug=73 |vitK_ug=24| right=1 | source_usda=1 |note=Vit. K [cite journal
author =Molly Damon, Nancy Z. Zhang, David B. Haytowitz, Sarah L. Booth
title =Phylloquinone (vitamin K₁) content of vegetables
journal =Journal of Food Composition and Analysis
volume =18
pages =751–758
publisher =Elsevier
date =2005
doi =10.1016/j.jfca.2004.07.004]

Lettuce ("Lactuca sativa") is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. In many countries, it is typically eaten cold and raw, in salads, hamburgers, tacos, and many other dishes. In some places, including China, lettuce is typically eaten cooked and use of the stem is as important as use of the leaf. Both the English name and the Latin name of the genus are ultimately derived from "lac", the Latin word for “milk”, [cite book | last = Simpson | first = D.P. | title = Cassell's Latin Dictionary | publisher = Cassell Ltd. | date = 1979 | edition = 5 | location = London | pages = 883 | id = ISBN 0-304-52257-0] referring to the plant’s milky juice. Mild in flavour, it has been described over the centuries as a cooling counterbalance to other ingredients in a salad.Grigson, p. 313] In his humorous essay "100 Things I Hate", filmmaker John Waters refers to iceberg lettuce as "the polyester of greens". [cite book |last=Waters|first=John |authorlink=John Waters (filmmaker) |title=Crackpot: the Obsessions of John Waters |year=1987 |publisher=Vintage|isbn=0394755340]

Description

The lettuce plant has a short stem initially (a rosette growth habit), but when it blooms the stem lengthens and branches, and it produces many flower heads that look like those of dandelions, but smaller. This is called . When grown to eat, lettuce is harvested before it bolts. Lettuce is used as a food plant by the larvae of some Lepidoptera. The largest lettuce head, of the Salad Bowl cultivar, weighed 11 kg (25 lb) grown by Colin Bowcock of Willaston, England, in 1974.

Cultivation

Lettuce is grown commercially worldwide. Hardy to Zone 6. Light, sandy, humus rich, moist soil. Dislikes dry conditions and can cause plants to bolt (go to seed). Early and late sowing in sunny positions or summer crops in shadecite web |url=http://www.pfaf.org/database/plants.php?Lactuca+sativa|title=Plants for a Future: Lactuca sativa|accessdate=2008-9-29] . It is considered fairly easy to grow and a suitable crop for beginners. [cite web |url=http://www.motherearthnews.com/Organic-Gardening/2006-12-01/10-Best-Garden-Crops-for-Beginners.aspx|title=Mother Earth News: 10 Best Garden Crops for Beginners|accessdate=2008-9-29]

Planting Depth: Some resources suggest planting seeds by covering lightly with soilcite book | last = Ashworth | first = Suzanne | title = Seed to Seed | publisher = Seed Savers Exchange | date = 2002 | id = ISBN 1-882424-58-0] while others suggest a depth of 1/4 to 1/2 inchcite web |url=http://www.urbanext.uiuc.edu/veggies/lettuce1.html|title=University of Illinois Extension: Lettuce|accessdate=2008-9-29]

Planting Spacing: Thin seedlings to 10 cm (4 in) apart for leaf lettuce [1 sq. m (9/sq ft)] and 6 to 8 inches apart for Cos or Butterhead (4/sq ft - 1/sq ft), transplant Crisphead seedlings 10 to 12 inches apart in the row (1/sq ft).

Row Spacing: 12 - 18 inches apart

History

The earliest depiction of lettuce is in the carvings at the temple of Senusret I at Karnak, where he offers milk to the god Min, to whom the lettuces was sacred. Later, Ancient Greek physicians believed lettuce could act as a sleep-inducing agent. The Romans cultivated it, and it eventually made its way to France cultivated of the Papal Court at Avignon.Grigson, p. 312] Christopher Columbus introduced lettuce to the new world. [cite web |url=http://www.foodreference.com/html/artlettuce.html|title=Lettuce:Food Facts & Trivia|accessdate=2007-11-02]

Cultivars

There are six commonly recognised Cultivar Groups of lettuce which are ordered here by head formation and leaf structure; there are hundreds of cultivars of lettuce selected for leaf shape and colour, as well as extended field and shelf life, within each of these Cultivar Groups:
*Butterhead forms loose heads; it has a buttery texture. Butterhead cultivars are most popular in Europe. Popular varieties include Boston, Bibb, Buttercrunch, and Tom Thumb.
*Chinese lettuce types generally have long, sword-shaped, non-head-forming leaves, with a bitter and robust flavour unlike Western types, appropriate for use in stir-fried dishes and stews. Chinese lettuce cultivars are divided into “stem-use” types (called celtuce in English), and “leaf-use” types such as "youmaicai" (zh-cp|c=油麦菜|p=yóumàicài) or "shengcai" (生菜).
*Crisphead, also called Iceberg, which form tight, dense heads that resemble cabbage. They are generally the mildest of the lettuces, valued more for their crunchy texture than for flavour. Cultivars of iceberg lettuce are the most familiar lettuces in the USA. The name Iceberg comes from the way the lettuce was transported in the US starting in the 1920s on train-wagons covered in crushed ice, making them look like icebergsFact|date=August 2008.
*Looseleaf, with tender, delicate, and mildly flavoured leaves. This group comprises oak leaf and lollo rosso lettuces.
*Romaine, also called Cos, grows in a long head of sturdy leaves with a firm rib down the center. Unlike most lettuces, it is tolerant of heat.
*Summer Crisp, also called Batavian, which form moderately dense heads with a crunchy texture; this type is intermediate between iceberg and looseleaf types.

Some lettuces (especially iceberg) have been specifically bred to remove the bitterness from their leaves. These lettuces have a high water content with very little nutrient value. Fact|date=January 2008 The more bitter lettuces and the ones with pigmented leaves contain antioxidants. Fact|date=January 2008

Breeding

"L. sativa" can easily be bred with closely related species in "Lactuca" such as "L. serriola", "L. saligna", and "L. virosa", and breeding programs for cultivated lettuce have included those species to broaden the available gene pool. Starting in the 1990s, breeding programs began to include more distantly related species such as "L. tatarica". [cite web | url = http://www.amjbot.org/cgi/content/full/85/11/1517 | title = Phylogenetic relationships among Lactuca (Asteraceae) species and related genera based on ITS-1 DNA sequences | author = Wim J. M. Koopman, Eli Guetta, Clemens C. M. van de Wiel, Ben Vosman and Ronald G. van den Berg | journal = American Journal of Botany | year = 1998 | volume = 85 | pages = 1517–1530]

eed Saving

Inbreeding plant, flowers form in heads of 10-25 individual florets of perfect flowers. Considered suitable for seed-saving beginners [cite web |url=http://www.seedsave.org/issi/904/beginner.html#anchor002|title=I n t e r n a t i o n a l S e e d S a v i n g I n s t i t u t e - Lettuce|accessdate=2008-9-29]

Nutrition

Lettuce is a fat free, low calorie food. It is a valuable source of vitamin A and folic acid. Lactucarium (or “Lettuce Opium”) is a mild opiate-like substance that is contained in all types of lettuce. Both the Romans and Egyptians took advantage of this property eating lettuce at the end of a meal to induce sleep. [ [http://www.selfsufficientish.com/lettuce.htm "Lettuce - "Lactuca sativa" - Daisy family"] . Hamilton, Dave (2005).]

Religious restrictions

The Yazidi of northern Iraq consider eating lettuce taboo. [cite news |url=http://query.nytimes.com/gst/fullpage.html?res=9B00E5DF1E3FF930A35752C0A9659C8B63&sec=&spon=&pagewanted=all |title=Bashiqa Journal: A Sect Shuns Lettuce and Gives the Devil His Due |first=Neill |last=MacFarquhar |authorlink=Neil MacFarquhar |work=The New York Times |date=2003-01-03 |accessdate=2008-03-31]

Notes

* [http://vric.ucdavis.edu/selectnewcrop.lettuce.htm "Iceberg and Leaf Lettuce"] , University of California

Cited text

*cite book |last=Grigson |first=Jane |authorlink=Jane Grigson |title=The Vegetable Book |year=1978 |publisher=Penguin |location=London |isbn=0-14-046-352-6