Lime

The key lime tree is a small, bushy, thorny evergreen reaching 3 to 5 metres, with small oval leaves and clusters of white flowers. Its round fruit is about 3 to 5 centimetres across, with a thin green to yellow rind, very aromatic and sharply acidic juice. Each fruit has up to about ten small seeds, cream to tan, plump and ovoid, 6 to 9 millimetres long, with a pointed end and slippery surface. Seeds are bitter and are removed in cooking. They are sold in packets for gardeners and nurseries. Lime seeds are typically polyembryonic, meaning one seed can give rise to several seedlings that are usually clones of the parent.

The true lime comes from tropical Southeast Asia, possibly the Indo-Malayan region, where it arose as a natural hybrid of citron with Citrus micrantha or related wild species. Arab traders took it to the Middle East, North Africa and Mediterranean, and Spanish and Portuguese explorers took it across the Atlantic in the sixteenth century. The English word lime comes through French and Spanish lima from Arabic limah and Persian limu, which also gave lemon. Key lime is named after the Florida Keys, where it was commercially grown from the nineteenth century.

Lime reached the Mediterranean through Arab trade by the tenth century and was grown in Spain, where it flourished in orchards. Spanish explorers took seed to the Caribbean, Mexico and Florida, and it became naturalised in warm regions such as the Florida Keys and the West Indies, which led to the names West Indian and key lime.

Limes became important at sea in the nineteenth century when the British Royal Navy shifted from lemons to limes to prevent scurvy, using West Indian lime juice, which led to British sailors being nicknamed limeys. Ironically, West Indian limes contain less vitamin C than lemons, and scurvy returned until the real cause was understood in the twentieth century.

Key limes were grown commercially in the Florida Keys until a hurricane in 1926 destroyed the groves, after which the Persian lime, a seedless hybrid, replaced them in markets. Key lime pie, a dessert made with condensed milk, remained a regional icon. In Mexico, key limes remain widely grown, and seed-grown trees produce the small aromatic fruit used in cooking. Seeds continue to be used by gardeners and nurseries as rootstock material.

Lime seeds are used to grow new trees and rootstocks, and potted seedlings are grown as ornamental houseplants. Folk uses include seed tea or ground seed in traditional remedies for digestion, though this is not well documented. Cooks occasionally use the seeds for their pectin when making marmalades. The fruit is the main culinary part, where juice and zest flavour cocktails, ceviche, curries, pies, marinades, salsas, soft drinks and pickles, and dried limes (loomi) are used in Middle Eastern stews. The peel provides essential oil for perfumery and flavouring.

Lime juice provides vitamin C and flavonoids, and the peel oils contain limonene and other terpenes. Seeds contain limonoids and phenolic compounds that have been studied in the laboratory for antioxidant and antimicrobial effects, but human data do not exist to support their use as a supplement. Food use of the fruit in normal amounts is considered healthy, and the seeds are not an established source of nutrition.