Key lime

The Key lime, also known as West Indian lime, Mexican lime, or Egyptian lime (Citrus × aurantiifolia or C. aurantifolia) is a type of lime. While it is treated as a species in botanical classification, it originated as a natural hybrid between Citrus micrantha (a wild papeda) and Citrus medica (citron).

The Key lime has thinner rind and is smaller, seedier, more acidic, and more aromatic than the Persian lime (Citrus × latifolia). It is valued for its characteristic flavor. The name comes from its association with the Florida Keys, where it is best known as the flavoring ingredient in Key lime pie. The Key lime is not to be confused with bartender's lime or the Omani lime, which are slightly different. The last is classified as a distinct race, with a thicker skin and darker green color. Philippine varieties have various names, including "dayap" and "bilolo".

The English word lime was derived, via Spanish then French, from the Arabic word ليمة līma, which is, in turn, a derivation of the Persian word limu لیمو. Key is from Florida Keys, where the fruit was naturalized. 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. aurantiifolia is a shrubby tree, growing to 5 metres (16 feet), 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 are ovate, 2.5–9 centimetres (1–3+1⁄2 inches) long, resembling orange leaves (the scientific name aurantiifolia referring to this resemblance to the leaves of Citrus aurantium). The flowers are 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.

Termed small-fruited acid lime (as opposed to large-fruited acid lime (Tahitian or Persian lime) it has a spherical fruit, 3-6 cm in diameter, sometimes with apical papillae, greenish-yellow; peel very thin, very densely glandular; segments with yellow-green pulp-vesicles, very acid, juicy and fragrant. Seeds are small, plump, ovoid, pale, smooth with white embryos (polyembryonic). The Key lime is usually picked while it is still green, but it becomes yellow when ripe.

Skin contact can sometimes cause phytophotodermatitis, which makes the skin especially sensitive to ultraviolet light.

'Mexican' lime and its clonal derivatives like 'West Indian' lime, 'Kagzi' lime and 'Key' lime are the most common cultivars of Citrus aurantifolia. Other small-fruited acid limes are cultivated in certain regions only; examples are, 'Abhayapuri' lime, 'Everglade' lime, 'Egyptian' lime, and 'India' lime.

The Key lime has given rise to several other lime varieties. The best known, the triploid progeny of a Key lime-lemon cross, is the Persian lime (Citrus × latifolia), the most widely produced lime, globally. Others are, like their parent, classed within C. aurantiifolia. Backcrossing with citron 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-pomelo 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 Giant Key lime. The potential to produce a wider variety of lime hybrids from the Key lime due to its tendency to form diploid gametes may reduce the disease risk presented by the limited diversity of the current commercial limes.