Orange (fruit)

• 1. Introduction

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  The orange began as something that did not exist in nature. It was coaxed into being through domestication in East Asia, a deliberate cross between two very different fruits: the mandarin orange and the pomelo. That original hybrid gave rise to every variety of sweet orange on earth today. None of them are wild. All are descended from a single prototype cross.

  In 314 BC, Chinese writers were already noting the fruit in their literature. Centuries later, a Spanish navigator may have planted orange trees on a Caribbean island, and a botanist sailing with a Vancouver Expedition collected seeds in South Africa and handed them to Hawaiian chiefs. Louis XIV of France kept potted orange trees in solid silver tubs inside the Palace of Versailles. In 1888, the United States government sent an entomologist to Australia to find a beetle that could save California's orange groves from destruction.

  This is a fruit whose biography spans continents, courts, and laboratories. What drove this humble citrus tree to become one of the most cultivated fruit trees on earth? How did it move from the orchards of Song dynasty China to the grand royal conservatories of France, and then to 67 million tonnes of global production in a single year?

• 2. A Fruit Built by Human Hands

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  Genomic analysis has revealed a precise portrait of the sweet orange's parentage: approximately 42% pomelo and 58% mandarin. That balance tells a more complicated story than a simple cross between the two parent species. The fruit was likely created from a mandarin orange that was not genetically pure, crossed with a pomelo that already carried substantial mandarin ancestry.

  Because the chloroplast genome of the sweet orange is that of the pomelo, scientists conclude the maternal parent was on the pomelo side of that cross, perhaps a backcross between a pomelo and a mandarin. What emerged was Citrus x sinensis, a hybrid so stable that every variety of sweet orange grown today, from navels to blood oranges, traces back to that single founding cross. The differences between varieties come not from new crosses but from mutations selected during centuries of agricultural propagation.

  The sweet orange also went on to father further hybrids. The grapefruit arose from a backcross between a sweet orange and a pomelo. Crosses with mandarin oranges and tangerines produced the clementine and the murcott. The ambersweet is a more complex layering: sweet orange crossed with an Orlando tangelo crossed with a clementine. Citrus taxonomy has proven notoriously difficult precisely because so many of these fruits are almost entirely interfertile with one another.

• 3. How a Fruit Crossed the World

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  In the 9th century, citrus fruits reached Sicily during the period of the Emirate of Sicily, but the sweet orange specifically remained unknown there until the late 15th century or the early 16th century, when Italian and Portuguese merchants carried the trees into the Mediterranean. Within decades, the fruit moved from obscurity to luxury status across Europe.

  By 1646, the sweet orange was well known throughout the continent. Louis XIV's appetite for orange trees reshaped architecture: the Orangerie at the Palace of Versailles was completed in 1686, allowing the court to grow the fruit year-round. When Louis condemned his finance minister Nicolas Fouquet in 1664, part of what he seized were more than 1,000 orange trees from Fouquet's estate at Vaux-le-Vicomte.

  Christopher Columbus may have planted orange trees on Hispaniola during his second voyage in 1493. By the mid-1500s, expeditions had carried the fruit to South America and Mexico. Pedro Menendez de Aviles brought the sweet orange to Florida in 1565 when he founded St. Augustine. Spanish missionaries reached Arizona between 1707 and 1710, and the Franciscans planted orange trees in San Diego, California, in 1769. Archibald Menzies, the botanist on the Vancouver Expedition, collected orange seeds in South Africa, raised the seedlings aboard ship, and gave them to several Hawaiian chiefs in 1792. The sweet orange spread across the Hawaiian Islands before the arrival of the Mediterranean fruit fly in the early 1900s ended its cultivation there.

• 4. California's Orange Empire

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  Jean-Louis Vignes likely planted the first private orange grove in Los Angeles in 1834. William Wolfskill followed in 1841, and by 1862 his orchards held two-thirds of all orange trees in California. Wolfskill's reported profits of $1,000 per acre in the early 1870s drew Midwestern farmers into the citrus trade, particularly in Orange County.

  In 1873, the U.S. Department of Agriculture distributed navel orange plants from Brazil. Luther C. Tibbets and Eliza Tibbets successfully cultivated these in Riverside, and the sweet, seedless navel orange became the backbone of California's citrus industry. Three years later, in 1876, the Valencia orange arrived; it matured in summer and fall, complementing the winter-ripening navel and supplying oranges across the full year.

  The completion of the Southern Pacific railroad in 1877 and the Santa Fe in 1885, along with the introduction of ventilated boxcars, opened national markets. Between 1875 and 1885 alone, the number of citrus trees in California grew from 90,000 to 2 million, reaching 4.5 million by 1901. A severe freeze across southern California in January 1913 destroyed a whole crop and spurred the development of smudge pots, fuel-burning heaters placed between trees to protect against frost.

  The University of California established its Citrus Experiment Station in 1907. Cooperative marketing took shape the same decade with the California Fruit Growers Exchange, formed in 1905 and later known as Sunkist Growers Inc.

• 5. Pests, Disease, and Biological Control

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  The cottony cushion scale, Icerya purchasi, arrived in California from Australia in 1868 and within 20 years had wiped out citrus orchards around Los Angeles. In 1888, the USDA sent Alfred Koebele to Australia to study the insect in its native habitat. He returned with specimens of an Australian ladybird, Novius cardinalis, commonly called the Vedalia beetle, and within a decade the pest was under control. This episode is recognized as one of the first successful applications of biological pest control on any crop.

  A more recent and more severe threat has been citrus greening disease, caused by the bacterium Liberobacter asiaticum, which has been the most serious danger to orange production since 2010. In areas where the disease is established, trees live for only five to eight years and never produce fruit suitable for eating. The disease was discovered in Florida in 1998 and has affected nearly all trees there since. It was reported in Brazil by Fundecitrus Brasil in 2004. By 2009, 0.87% of trees in Brazil's main growing areas in Sao Paulo and Minas Gerais showed symptoms, an increase of 49% over the previous year.

  The bacterium spreads primarily through the Asian citrus psyllid, Diaphorina citri Kuwayama. Foliar insecticides reduce psyllid populations temporarily but also suppress the beneficial predatory ladybirds that help keep the pest in check, repeating in miniature the same tension between chemical and biological control that Koebele's 1888 mission first exposed.

• 6. Naming, Flavor, and the Chemistry Within

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  The word "orange" traces back through Old French pomme d'orenge, through Persian and Arabic forms, to Sanskrit naraṅga, meaning orange tree, a word that belongs to the Dravidian language family of South India. In French, the initial n from the older form norenge was likely mistaken as part of the indefinite article, turning une norenge into une orenge. Linguists call this process juncture loss. The color itself was named after the fruit; the first recorded use of orange as a color name in English dates to 1512.

  The taste of an orange is governed by the ratio of sugars to acids. Bitter limonoid compounds, including limonin, decrease gradually as the fruit develops, while volatile aroma compounds tend to peak in mid- to late-season. Oranges are acidic, with pH levels ranging from 2.9 to 4.0. Ripe oranges often retain green patches even when fully mature, because the orange is a non-climacteric fruit: it does not ripen further once removed from the tree, and its skin color responds to ethylene gas through a process called degreening rather than through internal ripening chemistry.

  Sweet orange oil, a by-product of the juice industry made by pressing the peel, is approximately 90% D-limonene. This compound serves as a solvent in household products such as wood conditioners and detergents. The oil is promoted for being environmentally preferable to petrochemicals, though it is irritating to the skin and toxic to aquatic life.

• 7. Oranges in Art and Culture

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  Zhao Lingrang's Song dynasty fan painting Yellow Oranges and Green Tangerines attended not to the color of the fruit itself but to the shape of the fruit-laden trees. The poet Su Shi wrote of the same scene: "You must remember, / the best scenery of the year, / Is exactly now, / when oranges turn yellow and tangerines green."

  In Italian art and literature, the scholar Cristina Mazzoni has traced a range of meanings: oranges carried associations with desire and wealth on one hand, and deformity on the other. Catherine of Siena sent candied oranges to Pope Urban. Sandro Botticelli set his painting Primavera in an orange grove. In the fairy-stories of Sicily, the fruit held magical properties.

  In Western painting, Jan van Eyck's Arnolfini Portrait contains one of the earliest appearances of oranges, the costly fruit perhaps traded by the merchant Arnolfini himself. Vincent van Gogh painted his 1889 Still Life of Oranges and Lemons with Blue Gloves and his 1890 A Child with Orange, both late works. John Sloan's 1935 Blond Nude with Orange, Blue Couch came from the American Ashcan School. Henri Matisse's final painting, completed in 1951, was Nude with Oranges; after that work, he made only cut-outs.

  Mary Kettilby wrote the first marmalade recipe in 1714, and Janet Keiller of Dundee added pieces of peel in the 1790s, introducing the distinctively bitter character that British marmalade is still known for.