Key Lime

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 acidic, 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.

C. aurantiifolia is native to Southeast Asia. Its apparent path of introduction was through the Middle East to North Africa, then to Sicily and Andalucia and then, via Spanish explorers, to the West Indies, including the Florida Keys. 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, Florida, and later California.

There are various approaches to the cultivation of Key limes. This variety of citrus 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. 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 or bitter orange to obtain strong root stocks. It is often advisable to graft the plants onto rootstocks with low susceptibility to gummosis 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 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".