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The Key lime or acid lime (''Citrus'' × ''aurantiifolia'' or ''C. aurantifolia'') is a citrus hybrid ('' C. hystrix'' × '' C. medica'') native to tropical
Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
. It has a spherical fruit, in diameter. The Key lime is usually picked while it is still green, but it becomes yellow when ripe. The Key lime has thinner rind and is smaller, seedier, more acidic and more aromatic than the
Persian lime Persian lime (''Citrus'' × ''latifolia''), also known by other common names such as seedless lime, Bearss lime and Tahiti lime, is a citrus fruit species of hybrid origin, known only in cultivation. The Persian lime is a triploid cross betwe ...
(''Citrus × latifolia''). It is valued for its characteristic flavor. The name comes from its association with the
Florida Keys The Florida Keys are a coral island, coral cay archipelago off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of Miami a ...
, where it is best known as the
flavoring A flavoring (or flavouring), also known as flavor (or flavour) or flavorant, is a food additive that is used to improve the taste or smell of food. It changes the perceptual impression of food as determined primarily by the chemoreceptors of ...
ingredient in
Key lime pie Key lime pie is an American dessert pie. It is made of Key lime juice, egg yolks, and sweetened condensed milk. It may be served with no topping, with a meringue topping made from egg whites, or with whipped cream. Traditionally, Key lime pie i ...
. The key lime is not to be confused with West Indian lime, bartender's lime, Omani lime, or Mexican lime which are slightly different. The last is classified as a distinct race with a thicker skin and darker green colour. Philippine varieties have various names, including ''dayap'' and ''bilolo''.


Etymology

The English word ''lime'' was derived, via
Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many countries in the Americas **Spanish cuisine **Spanish history **Spanish culture ...
then French, from the Arabic word ''līma'', which is, in turn, a derivation of the Persian word ''limu'' . ''Key'' is from
Florida Keys The Florida Keys are a coral island, coral cay archipelago off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of Miami a ...
, where the fruit was naturalised. The earliest known use of the name is from 1905, where the fruit was described as "the finest on the market. It is aromatic, juicy, and highly superior to the lemon."


Description

''C. aurantiifolia'' is a shrubby tree, growing to , with many thorns. Dwarf varieties exist that can be grown indoors during winter months and in colder climates. Its trunk, which rarely grows straight, has many branches, and they often originate quite far down on the trunk. The
leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...
are ovate, long, resembling orange leaves (the scientific name ''aurantiifolia'' referring to this resemblance to the leaves of ''
Citrus aurantium The bitter orange, sour orange, Seville orange, bigarade orange, or marmalade orange is the hybrid citrus tree species ''Citrus'' × ''aurantium'', and its fruit. It is native to Southeast Asia and has been spread by humans to many parts of th ...
''). The
flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...
s are in diameter, are yellowish white with a light purple tinge on the margins. Flowers and fruit appear throughout the year, but are most abundant from May to September in the Northern Hemisphere.''Citrus aurantiifolia'' Swingle
Hort.purdue.edu. Retrieved on 2011-06-19.
Skin contact can sometimes cause
phytophotodermatitis Phytophotodermatitis, also known as berloque dermatitis,, margarita photodermatitis,, lime disease or lime phytodermatitis is a cutaneous phototoxic inflammatory reaction resulting from contact with a light-sensitizing botanical agent (such as ...
, which makes the skin especially sensitive to
ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
light.


Taxonomy

The Key lime cultivar is a citrus hybrid, '' Citrus micrantha'' × '' Citrus medica'' (a papeda-
citron The citron (''Citrus medica''), historically cedrate, is a large fragrant citrus fruit with a thick Peel (fruit), rind. It is said to resemble a 'huge, rough lemon'. It is one of the Citrus taxonomy#Citrons, original citrus fruits from which al ...
cross). The Key lime has given rise to several other lime varieties. The best known, the
triploid Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one fro ...
progeny of a Key lime-lemon cross, is the
Persian lime Persian lime (''Citrus'' × ''latifolia''), also known by other common names such as seedless lime, Bearss lime and Tahiti lime, is a citrus fruit species of hybrid origin, known only in cultivation. The Persian lime is a triploid cross betwe ...
(''Citrus × latifolia''), the most widely produced lime, globally. Others are, like their parent, classed within ''C. aurantiifolia''. Backcrossing with
citron The citron (''Citrus medica''), historically cedrate, is a large fragrant citrus fruit with a thick Peel (fruit), rind. It is said to resemble a 'huge, rough lemon'. It is one of the Citrus taxonomy#Citrons, original citrus fruits from which al ...
has produced a distinct group of triploid limes that are also of commercial value to a limited degree, the seedy Tanepeo, Coppenrath, Ambilobe and Mohtasseb lime varieties as well as the Madagascar lemon. Hybridization with a
mandarin Mandarin or The Mandarin may refer to: Language * Mandarin Chinese, branch of Chinese originally spoken in northern parts of the country ** Standard Chinese or Modern Standard Mandarin, the official language of China ** Taiwanese Mandarin, Stand ...
-
pomelo The pomelo ( ; or pummelo, ''Citrus maxima''), also known as a shaddock, is the largest citrus fruit. It is an ancestor of several cultivated citrus species, including the bitter orange and the grapefruit. It is a natural, non-hybrid citrus fr ...
cross similar to the oranges has produced the Kirk lime. The New Caledonia and Kaghzi limes appear to have resulted from an F2 Key lime self-pollination, while a spontaneous genomic duplication gave us the
tetraploid Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one fro ...
Giant Key lime. The potential to produce a wider variety of lime hybrids from the Key lime due to its tendency to form
diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...
gametes may reduce the disease risk presented by the limited diversity of the current commercial limes.


Distribution and habitat

''C. aurantiifolia'' is native to
Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
. Its apparent path of introduction was through the
Middle East The Middle East (term originally coined in English language) is a geopolitical region encompassing the Arabian Peninsula, the Levant, Turkey, Egypt, Iran, and Iraq. The term came into widespread usage by the United Kingdom and western Eur ...
to
North Africa North Africa (sometimes Northern Africa) is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region. However, it is sometimes defined as stretching from the Atlantic shores of t ...
, then to
Sicily Sicily (Italian language, Italian and ), officially the Sicilian Region (), is an island in the central Mediterranean Sea, south of the Italian Peninsula in continental Europe and is one of the 20 regions of Italy, regions of Italy. With 4. ...
and
Andalucia Andalusia ( , ; , ) is the southernmost autonomous community in Peninsular Spain, located in the south of the Iberian Peninsula, in southwestern Europe. It is the most populous and the second-largest autonomous community in the country. It i ...
and then, via Spanish explorers, to the
West Indies The West Indies is an island subregion of the Americas, surrounded by the Atlantic Ocean, North Atlantic Ocean and the Caribbean Sea, which comprises 13 independent island country, island countries and 19 dependent territory, dependencies in thr ...
, including the
Florida Keys The Florida Keys are a coral island, coral cay archipelago off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of Miami a ...
. Henry Perrine is credited with introducing the Key lime to Florida. From the Caribbean, lime cultivation spread to tropical and subtropical North America, including
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
,
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
, and later
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
.


Cultivation


History

In California in the late 19th century, "Mexican" limes were more highly valued than lemons; however, in Florida, they were generally considered weeds. Then, in 1894–95, the Great Freeze destroyed the Florida lemon groves, and farmers replanted Mexican limes instead; they soon became known as the Florida Key Lime, a "beloved regional crop". But when the 1926 Miami hurricane ripped them up, they were replanted with the hardier, thornless Persian limes.Stella Parks. ''BraveTart: Iconic American Desserts'', 2017, , p. 171-173 Since the
North American Free Trade Agreement The North American Free Trade Agreement (, TLCAN; , ALÉNA), referred to colloquially in the Anglosphere as NAFTA, ( ) was an agreement signed by Canada, Mexico, and the United States that created a trilateral trade bloc in North America. The ...
came into effect, most Key limes on the United States market have been grown in Mexico,
Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...
and
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
. They are also grown in
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
, Florida, and California.


Propagation

There are various approaches to the cultivation of Key limes. This variety of
citrus ''Citrus'' is a genus of flowering trees and shrubs in the family Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, mandarins, lemons, grapefruits, pomelos, and limes. ''Citrus'' is nativ ...
can be propagated from seed and will grow true to the parent. The seeds must be kept moist until they can be planted, as they will not germinate if allowed to dry out. If the plants are propagated from seed, the seeds should be stored at least 5–6 months before planting.Duke J.A., duCellier J.L. (1993): ''CRC handbook of alternative cash crops'' (page 139-145) Alternatively, vegetative propagation from cuttings or by air layering may permit fruit production within one year, and from genetically more predictable lines of plants. Another method, digging around a mature tree to sever roots, will encourage new sprouts that can be transplanted to another location. Clones are often bud grafted into rough
lemon The lemon (''Citrus'' × ''limon'') is a species of small evergreen tree in the ''Citrus'' genus of the flowering plant family Rutaceae. A true lemon is a hybrid of the citron and the bitter orange. Its origins are uncertain, but some ...
or
bitter orange The bitter orange, sour orange, Seville orange, bigarade orange, or marmalade orange is the hybrid citrus tree species ''Citrus'' × ''aurantium'', and its fruit. It is native to Southeast Asia and has been spread by humans to many parts of th ...
to obtain strong root stocks. It is often advisable to graft the plants onto rootstocks with low susceptibility to
gummosis Gummosis is the formation of patches of a gummy substance on the surface of certain plants, particularly fruit trees. This occurs when sap oozes from wounds or cankers as a reaction to outside stimuli such as adverse weather conditions, infect ...
because seedlings generally are highly vulnerable to the disease. Useful rootstocks include wild grapefruit, cleopatra mandarin and tahiti limes. ''C. macrophylla'' is also sometimes used as a rootstock in Florida to add vigor. Climatic conditions and fruit maturation are crucial in cultivation of the lime tree. Under consistently warm conditions potted trees can be planted at any season, whereas in cooler temperate regions it is best to wait for the late winter or early spring. The Key lime tree does best in sunny sites, well-drained soils, good air circulation, and protection from cold wind. Because its root system is shallow, the Key lime is planted in trenches or into prepared and broken rocky soil to give the roots a better anchorage and improve the trees' wind resistance. Pruning and topping should be planned to maximise the circulation of air and provide plenty of sunlight. This keeps the crown healthily dry, improves accessibility for harvesting, and discourages the organisms that cause gummosis.


Harvesting

The method of cultivation greatly affects the size and quality of the harvest. Trees cultivated from seedlings take 4–8 years before producing a harvest. They attain their maximal yield at about 10 years of age. Trees produced from cuttings and air layering bear fruit much sooner, sometimes producing fruit (though not a serious harvest) a year after planting. It takes approximately 9 months from the blossom to the fruit. When the fruit have grown to harvesting size and begin to turn yellow they are picked and not clipped. To achieve produce of the highest market value, it is important not to pick the fruit too early in the morning; the turgor is high then, and handling turgid fruit releases the peel oils and may cause spoilage.


Postharvest process

Shelf life Shelf life is the length of time that a commodity may be stored without becoming unfit for use, consumption, or sale. In other words, it might refer to whether a commodity should no longer be on a pantry shelf (unfit for use), or no longer on a s ...
of Key limes is an important consideration in marketing. The lime still ripens for a considerable time after harvesting, and it is usually stored between at a
relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog t ...
of 75–85%. Special procedures are employed to control the shelf life; for example, applications of growth regulators, fruit wax,
fungicide Fungicides are pesticides used to kill parasitic fungi or their spores. Fungi can cause serious damage in agriculture, resulting in losses of yield and quality. Fungicides are used both in agriculture and to fight fungal infections in animals, ...
s, precise cooling, calcium compounds,
silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar causti ...
, and special packing material. The preferred storage conditions are temperatures of and a humidity over 85%, but even in ideal conditions post-harvesting losses are high. In India most Key lime producers are small-scale farmers without access to such post-harvesting facilities, but makeshift expedients can be of value. One successful procedure is a coating of
coconut oil Coconut oil (or coconut fat) is an edible oil derived from the kernels, meat, and milk of the coconut palm fruit. Coconut oil is a white solid fat below around , and a clear thin liquid oil at higher temperatures. Unrefined varieties have a disti ...
that improves shelf life, thereby achieving a constant market supply of Key limes.Bisen A., Pandey S.K., Patel N.: ''Effect of skin coatings on prolonging shelf life of kagzi lime fruits (Citrus aurantiifolia Swingle).'' Journal of Food Science and Technology (2012) 49(6).753-759. (page 139–145) Key limes are made into black lime by boiling them in
brine Brine (or briny water) is a high-concentration solution of salt (typically sodium chloride or calcium chloride) in water. In diverse contexts, ''brine'' may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawat ...
and drying them. Black lime is a condiment commonly used in the Middle East.


Yield

The yield varies depending on the age of the trees. Five- to seven-year-old orchards may yield about 6 t/ha (2.7 tons/acre), with harvests increasing progressively until they stabilise at about 12–18 t/ha (5.4–8 tons/acre). Seedling trees take longer to attain their maximal harvest, but eventually out-yield grafted trees.


In culture

The annual Key Lime Festival in
Key West, Florida Key West is an island in the Straits of Florida, at the southern end of the U.S. state of Florida. Together with all or parts of the separate islands of Sigsbee Park, Dredgers Key, Fleming Key, Sunset Key, and the northern part of Stock Islan ...
, has been held every year since 2002 over the
Independence Day An independence day is an annual event memorialization, commemorating the anniversary of a nation's independence or Sovereign state, statehood, usually after ceasing to be a group or part of another nation or state, or after the end of a milit ...
weekend and is a celebration of Key limes in food, drinks, and culture, with a significant emphasis on
Key lime pie Key lime pie is an American dessert pie. It is made of Key lime juice, egg yolks, and sweetened condensed milk. It may be served with no topping, with a meringue topping made from egg whites, or with whipped cream. Traditionally, Key lime pie i ...
.


References


External links

* *
Citrus aurantiifolia (Christm.) Swingle
United States Forest Service The United States Forest Service (USFS) is an agency within the United States Department of Agriculture, U.S. Department of Agriculture. It administers the nation's 154 United States National Forest, national forests and 20 United States Natio ...
description
Key Lime Tree History

Characterization of limes (Citrus aurantifolia) grown in Bhutan and Indonesia using high-throughput sequencing
{{Authority control Citrus Citrus hybrids Fruit trees Limes (fruit)