From The Plant Encyclopedia
Citrus, Oranges, Lemons, Grapefruit, Limes
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|Sweet Orange (Citrus × sinensis cultivar)|
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- Cultivation: For-Gardeners
- Light: Sun
- Soil: Rich
- pH: 7
- Moisture: Medium
- Form: Tree
- Habit: Evergreen
- Flower: Medium
- Fruit/Seed: Large
- Foliage: Leaves, Green
- Uses: Edible, Ornamental, Industrial, Houseplant
Citrus is a common term and Genus (Citrus) of Flowering plants in the Rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar (Burma) and the Yunnan province of China. Citrus fruit has been cultivated in an ever-widening area since ancient times; the most well known examples are the oranges, Lemons, Grapefruit and limes.
The generic name originated in Latin, where it specifically referred to the plant now known as Citron (C. medica). It was derived from the Ancient Greek word for cedar, kεδρος (kedros). Some believe this was because Hellenistic Jews used the fruits of C. medica during Sukkot (Feast of the Tabernacles) in place of a cedar cone, while others state it was due to similarities in the smell of citrus leaves and fruit with that of cedar. Collectively, Citrus fruits and plants are also known by the Romance Loanword agrumes (literally "sour fruits").
The Taxonomy and Systematics of the genus are complex and the precise number of natural Species is unclear, as many of the named species are Clonally propagated hybrids, and there is Genetic evidence that even some wild, true-breeding species are of hybrid origin. Cultivated Citrus may be derived from as few as four ancestral species. Natural and cultivated origin hybrids include commercially important Fruit such as the oranges, grapefruit, lemons, some limes, and some tangerines.
Research suggests that the closely related genus Fortunella (kumquats), and perhaps also Poncirus and the Australian Microcitrus and Eremocitrus, should be included in Citrus; most botanists now classify Microcitrus and Eremocitrus as part of the genus Citrus. Two additional genera: Triphasia and Clymenia are likewise very closely related, and bear hesperidium fruits, but are not considered part of the Citrus genus. At least one, Clymenia, will hybridize with Kumquats and some Limes.
List of Popular Cultivated Citrus Fruits
The genus Citrus has been suggested to originate in Southeast Asia. Prior to human cultivation, it consisted of just a few species, namely:
Citrus aurantifolia Omani Lime, from India
Citrus maxima (pummelo, shaddock), from the Malay Archipelago
Citrus medica from India
Citrus reticulata – Mandarin orange, from China
Citrus trifoliata – Trifoliate Orange, from Korea and adjacent China (often separated as Poncirus)
Citrus australasica – Finger Lime (sometimes separated in Microcitrus)
Citrus australis – Australian Round Lime (sometimes separated in Microcitrus)
Citrus glauca – Desert Lime (sometimes separated in Eremocitrus)
and 3 other Microcitrus
Kumquats, 4-5 species from East Asia ranging into Southeast Asia (often separated as Fortunella)
Citrus halimii – Limau kadangsa, Limau kedut kera, from Thailand and Malaya
Citrus indica – Indian Wild Orange, from the Indian subcontinent
Citrus macroptera from Indochina and Melanesia
"Khasi Papeda" – Citrus latipes from Assam, Meghalaya, Burma
Citrus fruits are notable for their fragrance, partly due to Flavonoids and Limonoids (which in turn are Terpenes) contained in the rind, and most are juice-laden. The juice contains a high quantity of Citric acid giving them their characteristic sharp flavour. They are also good sources of Vitamin C and Flavonoids.
The colour of citrus fruits only develops in climates with a (diurnal) cool winter. In tropical regions with no winter at all, citrus fruits remain green until maturity, hence the tropical "green oranges". The Persian Lime in particular is extremely sensitive to cool conditions, thus it is not usually exposed to cool enough conditions to develop a mature colour. If they are left in a cool place over winter, the fruits will change colour to yellow.
The terms "ripe" and "mature" are usually used synonymously, but they mean different things. A mature fruit is one that has completed its growth phase. Ripening is the term used to describe the changes that occur within the fruit after it is mature to the beginning of decay. These changes usually involve starches converting to sugars, a decrease in acids and a softening and change in the fruit's colour.
Citrus fruits are non-Climacteric and respiration slowly declines and the production and release of ethylene is gradual. The fruits do not go through a ripening process in the sense that they become "tree ripe." Some fruits, for example cherries, physically mature and then continue to ripen on the tree. Other fruits, like pears, are picked when mature but before they ripen, then continue to ripen off the tree. Citrus fruits pass from immaturity to maturity to over-maturity while still on the tree. Once they are separated from the tree, they will not increase in sweetness or continue to ripen. The only way change may happen after being picked is that they will eventually start to decay.
With oranges, colour cannot be used as an indicator of ripeness because sometimes the rinds turn orange long before the oranges are ready to eat. Tasting them is the only way to know whether or not they are ready to eat.
Major commercial citrus growing areas include southern China, the Mediterranean Basin (including southern Spain), South Africa, Australia, the southernmost United States and parts of South America. In the United States, Florida, California, Arizona, and Texas are major producers, while smaller plantings are present in other Sun Belt states.
As ornamental plants
Citrus trees grown in tubs and wintered under cover were a feature of Renaissance gardens, once glass-making technology enabled sufficient expanses of clear glass to be produced. An Orangery was a feature of royal and aristocratic residences through the 17th and 18th centuries. The Orangerie at the Palace of the Louvre, 1617, inspired imitations that were not eclipsed until the development of the modern greenhouse in the 1840s. In the United States the earliest surviving orangery is at the Tayloe House, Mount Airy, Virginia. George Washington had an orangery at Mount Vernon.
Some modern hobbyists still grow dwarf citrus in containers or greenhouses in areas where it is too cold to grow it outdoors. Consistent climate, sufficient sunlight, and proper watering are crucial if the trees are to thrive and produce fruit. Compared to many of the usual "green shrubs", citrus trees better tolerate poor container care. For cooler winter areas, limes and Lemons should not be grown, since they are more sensitive to winter cold than other citrus fruits. Hybrids with Kumquats (× Citrofortunella) have good cold resistance.
Pests and diseases
European brown snails (Helix aspersa) can be a problem in California, though laying female Khaki Campbell and other Mallard-based Ducks can be used for control.
The foliage is also used as a food plant by the Larvae of Lepidoptera (Butterfly and Moth) species such as the Geometridae Common Emerald (Hemithea aestivaria) and Double-striped Pug (Gymnoscelis rufifasciata), the Arctiidae Giant Leopard Moth (Hypercompe scribonia), H. eridanus, H. icasia and H. indecisa, many species in the family Papilionidae (swallowtail butterflies), and the Black-lyre Leafroller Moth ("Cnephasia" jactatana), a Tortrix moth.
Since 2000, the Citrus Leafminer (Phyllocnistis citrella) has been a pest in California, boring meandering patterns through leaves.
In eastern Australia, the Bronze-orange Bug (Musgraveia sulciventris) can be a major pest of citrus trees, particularly grapefruit. In heavy infestations it can cause flower and fruit drop and general tree stress.
Citrus juice also has medical uses; lemon juice is used to relieve the pain of Bee stings. Oranges were historically used for their high content of Vitamin C, which prevents Scurvy. Scurvy is caused by vitamin C deficiency, and can be prevented by having 10 milligrams of vitamin C a day. An early sign of scurvy is fatigue. If ignored, later symptoms are bleeding and bruising easily. British sailors were given a ration of citrus fruits on long voyages to prevent the onset of scurvy, hence the British nickname of Limey.
After consumption, the peel is sometimes used as a facial cleanser. A peel of lemons or orange is commonly used as a means to moisten Medical cannabis when stored with it. Before the development of fermentation-based processes, lemons were the primary commercial source of Citric acid.
Citrus fruit juices, such as orange, lime and lemon, may be useful for lowering the risk factors for specific types of Kidney stones. Orange juice may help prevent Calcium oxalate stone formation. Lemons have the highest concentration of citrate of any citrus fruit, and daily consumption of Lemonade has been shown to decrease the rate of stone formation.
- (1961): Acclimatization of citrus fruits in the Mediterranean region. Agricultural History 35(1): 35-46.
- (2003): What is Citrus? Taxonomic implications from a study of cp-DNA evolution in the tribe Citreae (Rutaceae subfamily Aurantioideae). Organisms Diversity & Evolution 3(1): 55-62. (HTML abstract)
- (2000): Citrus phylogeny and genetic origin of important species as investigated by molecular markers. Theoretical and Applied Genetics 100(8): 1155-1166. (HTML abstract)
33 ^ Carr, Jackie (April 22, 2010). "Five Ways to Prevent Kidney Stones". UC San Diego. http://health.ucsd.edu/news/2010/4-22-kidney-stones.htm. Retrieved 2010-12-03
- (2002): Origin and history. In: (2002): Citrus. Taylor & Francis. ISBN 0-415-28491-0
- (1985): Chapter 64. Rutaceae. In: Handbook of Seed Technology for Genebanks (Volume II: Compendium of Specific Germination Information and Test Recommendations). International Board for Plant Genetic Resources, Rome, Italy. HTML fulltext
- (1991): FAO/IBPGR Technical Guidelines for the Safe Movement of Citrus Germplasm. FAO, IOCV, IPGRI. PDF fulltext
- (1999): Descriptors for Citrus (Citrus spp.). PDF fulltext
- (2005): Purdue University Tropical Horticulture Lecture 32: Citrus
- (1995): RFLP analysis of cytoplasmic and nuclear genomes used for citrus taxonomy. In: Mandarines - développements scientifiques récents, résumés oraux et posters: 12-13. CIRAD-FLHOR, San Nicolao, France. HTML abstract
- (2000): Citrus, Proceedings of a regional workshop on disease management of banana and citrus through the use of disease-free planting materials held in Davao City, Philippines, 14–16 October 1998. INIBAP. PDF fulltext
- (2005): Orange Empire: California and the Fruits of Eden.
- (1967–1989): The Citrus Industry. HTML fulltext of Vol. 1, 2, & Vol. 5, Chapter 5
1 ^ Carr, Jackie (April 22, 2010). "Five Ways to Prevent Kidney Stones". UC San Diego. http://health.ucsd.edu/news/2010/4-22-kidney-stones.htm. Retrieved 2010-12-03. 1 ^ Carr, Jackie (April 22, 2010). "Five Ways to Prevent Kidney Stones". UC San Diego. http://health.ucsd.edu/news/2010/4-22-kidney-stones.htm. Retrieved 2010-12-03.
- Effects of pollination on Citrus plants Pollination of Citrus by Honey Bees
- Citrus Research and Education Center of IFAS (largest citrus research center in world)
- Citrus Variety Collection by the University of California
- Citrus (Mark Rieger, Professor of Horticulture, University of Georgia)
- Sorting Citrus names
- Fundecitrus - Fund for Citrus Plant Protection is an organization of citrus Brazilian producers and processors.
- Citrus - taxonomy, fruit anatomy at GeoChemBio
- Home Citrus Growers