Key lime

TheKey limeoracid lime(Citrus×aurantiifoliaorC. aurantifolia) is acitrus hybrid(C. hystrix×C. medica) native to tropicalSoutheast Asia. It has a spherical fruit, 2.5–5 centimetres (1–2 inches) in diameter. The Key lime is usually picked while it is still green, but it becomes yellow when ripe.
The Key lime has thinnerrindand is smaller, seedier, more acidic and more aromatic than thePersian lime(Citrus × latifolia). It is valued for its characteristic flavor. The name comes from its association with theFlorida Keys, where it is best known as theflavoringingredient inKey lime pie. Not to be confused withWest Indian lime,bartender's lime,Omani lime, orMexican limewhich are slightly different. The last classified as a distinctracewith a thicker skin and darker green colour. Philippine varieties have various names, includingdayapandbilolo.
The English wordlimewas derived, viaSpanishthenFrench, from the Arabic wordليمةlīma, which is, in turn, a derivation of thePersianwordlimuلیمو.Keyis fromFlorida Keys, 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."
C. aurantiifoliais a shrubby tree, growing to 5 metres (16 feet), with manythorns. Dwarfvarietiesexist 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. Theleavesare ovate,2.5–9 centimetres (1–3+1⁄2inches) long, resemblingorangeleaves (the scientific nameaurantiifoliareferring to this resemblance to the leaves ofCitrus aurantium). Theflowersare 2.5 cm (1 in) 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.
Skin contact can sometimes causephytophotodermatitis,which makes the skin especially sensitive toultravioletlight.
The Key lime cultivar is acitrus hybrid,Citrus micrantha×Citrus medica(apapeda-citroncross).
The Key lime has given rise to several other lime varieties.  The best known, thetriploidprogeny of a Key lime-lemon cross, is thePersian lime(Citrus × latifolia), the most widely produced lime, globally. Others are, like their parent, classed withinC. aurantiifolia.Backcrossingwithcitronhas 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 amandarin-pomelocross similar to the oranges has produced the Kirk lime. The New Caledonia and Kaghzi limes appear to have resulted from anF2Key lime self-pollination, while a spontaneous genomic duplication gave us thetetraploidGiant Key lime.The potential to produce a wider variety of lime hybrids from the Key lime due to its tendency to formdiploidgametes may reduce the disease risk presented by the limited diversity of the current commercial limes.
C. aurantiifoliais native toSoutheast Asia. Its apparent path of introduction was through theMiddle EasttoNorth Africa, then toSicilyandAndaluciaand then, via Spanish explorers, to theWest Indies, including theFlorida Keys.Henry Perrineis credited with introducing the Key lime to Florida.From the Caribbean, lime cultivation spread to tropical and subtropical North America, includingMexico,Florida, and laterCalifornia.
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, theGreat Freezedestroyed 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 the1926 Miami hurricaneripped them up, they were replanted with the hardier, thornless Persian limes.
Since theNorth American Free Trade Agreementcame into effect, most Key limes on the United States market have been grown in Mexico,Central AmericaandSouth America. They are also grown inTexas, Florida, and California.
There are various approaches to the cultivation of Key limes. This variety ofcitruscan 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.Alternatively, vegetative propagation from cuttings or byair layeringmay 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 graftedinto roughlemonorbitter orangeto obtain strong root stocks.
It is often advisable to graft the plants onto rootstocks with low susceptibility togummosisbecause seedlings generally are highly vulnerable to the disease. Useful rootstocks include wild grapefruit,cleopatra mandarinandtahiti limes.C. macrophyllais 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.
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.
Shelf lifeof Key limes is an important consideration in marketing. The lime still ripens for a considerable time after harvesting, and it is usually stored between 12.5 and 15.5 °C (55–60 °F) at arelative humidityof 75–85%. Special procedures are employed to control the shelf life; for example, applications ofgrowth regulators,fruit wax,fungicides, precise cooling, calcium compounds,silver nitrate, and special packing material. The preferred storage conditions are temperatures of 9–10 °C (48–50 °F) 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 ofcoconut oilthat improves shelf life, thereby achieving a constant market supply of Key limes.
Key limes are made intoblack limeby boiling them inbrineand drying them. Black lime is a condiment commonly used in the Middle East.
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.
The annual Key Lime Festival inKey West, Florida, has been held every year since 2002 over theIndependence Dayweekend and is a celebration of Key limes in food, drinks, and culture, with a significant emphasis onKey lime pie.