The citron is a large fragrant citrus fruit with thick rind, botanically classified as Citrus medica by both the Swingle and Tanaka botanical name systems. It is one of the only three original citrus fruit (the others being pummelo and mandarine), from which most other citrus types developed through natural or artificial hybridization.
The designation medica given it by Linnaeus, apparently is derived from its ancient name, "Median or Persian apple", that was reported by Theophrastus, who believed it to be native to Persia or the land of the Medes.
The fruit's name "citron" derives ultimately from Latin, citrus, also the origin of the genus name, and as a result it has many similar names in many European languages, e.g. cederat, cédrat, cedro, etc.
A source of confusion is that citron or similar words in French, Hungarian, Finnish, Latvian, the West Slavic languages, and all Germanic languages but English are false friends, as they refer to the lemon. Indeed, into the 16th century, the English name citron included the lemon and perhaps the lime as well.
In most Arabic languages it is called Turunj or similar, in Syria and many other Muslim countries Kabbad, in Japanese Bushkan (maybe referring only to the fingered varieties) and in Bangladesh Shatkore.
While the lemon or orange are peeled to consume their pulpy and juicy segments, the citron's pulp is dry, containing a small quantity of insipid juice, if any. The main content of a citron fruit is the thick white rind, which adheres to the segments, and cannot be separated from them easily. The citron gets halved and depulped, it's rind is cooked in sugar, diced into succade which is used as confection.
Today the citron is used for the fragrance or zest of its flavedo, but the most important part is still the inner rind (known as pith or albedo), which is a fairly important article in international trade and is widely employed in the food industry as succade, as it is known when it is candied in sugar.
From ancient through medieval times, the citron was used mainly for medical purposes: to combat seasickness, pulmonary troubles, intestinal ailments, scurvy and other disorders. The essential oil of the flavedo (the outermost, pigmented layer of rind) was also regarded as an antibiotic. Citron juice with wine was considered an effective antidote to poison, as Theophrastus reported. In Ayurvedic system of medicine, the fruit juice is still used for treating conditions like nausea, vomiting, excessive thirst etc.
The fruit juice has a high content of Vitamin C and used medicinally as an anthelminthic, appetizer, tonic, in cough, rheumatism, vomiting, flatulence, haemorrhoids, skin diseases and weak eye sight. There is a recent study that citron has some cardiovascular benefits.
There is a rising market for the citron for the use of its soluble fiber (pectin) found in its thick albedo. There are also scientific claims that modified citrus pectin can help even against cancer.
The citron is also used by Jews (the word for it in Hebrew is etrog) for a religious ritual during the Feast of Tabernacles; therefore is considered as a Jewish symbol, and is found on various Hebrew antiques and archeological findings. Citrons used for ritual purposes cannot be grown by grafting branches.
Description and variation
The citron fruit is usually ovate or oblong, narrowing towards the stylar end. However, the citron's fruit shape is highly variable, due to the large quantity of albedo, which forms independently according to the fruits' position on the tree, twig orientation, and many other factors. The rind is leathery, furrowed, and adherent. The inner portion is thick, white and fleshy; the outer is uniformly thin and very fragrant. The pulp is usually acidic, but also can be sweet, and even pulpless varieties are found.
Most citron varieties contain a large number of monoembryonic seeds. They are white, with dark innercoats and red-purplish chalazal spots for the acidic varieties, and colorless for the sweet ones. Some citron varieties are also distinct, having persistent styles, that do not fall off after fecundation. Those are usually promoted for etrog use.
Some citrons have medium-sized oil bubbles at the outer surface, medially distant to each other. Some varieties are ribbed and faintly warted on the outer surface. There is also a fingered citron variety called Buddha's hand.
The color varies from green, when unripe, to a yellow-orange when overripe. The citron does not fall off the tree and can reach 8–10 pounds (4–5 kg) if not picked before fully mature. However, they should be picked before the winter, as the branches might bend or break to the ground, and may cause numerous fungal diseases for the tree.
Citrus medica is a slow-growing shrub or small tree that reaches a height of about 8 to 15 ft (2 to 5 m). It has irregular straggling branches and stiff twigs and long spines at the leaf axils. The evergreen leaves are green and lemon-scented with slightly serrate edges, ovate-lanceolate or ovate elliptic 2.5 to 7.0 inches long. Petioles are usually wingless or with minor wings. The flowers are generally unisexual providing self-pollination, but some male individuals could be found due to pistil abortion. The clustered flowers of the acidic varieties are purplish tinted from outside, but the sweet ones are white-yellowish.
The citron tree is very vigorous with almost no dormancy, blooming several times a year, and is therefore fragile and extremely sensitive to frost.
Varieties & hybrids
The acidic varieties include the Florentine and Diamante citron from Italy, the Greek citron and the Balady citron from Israel. The sweet varieties include the Corsican and Moroccan citrons. Between the pulpless are also some fingered varieties and the Yemenite citron.
There are also a number of citron hybrids; for example, ponderosa lemon, the lumia and rhobs el Arsa are known citron hybrids, some are claiming that even the Florentine citron is not pure citron, but a citron hybrid.
Origin and distribution
Despite the variation among the cultivars, authorities agree the citron is an old and original species. There is molecular evidence that all other cultivated citrus species arose by hybridization among four ancestral types, which are the citron, pomelo, mandarin and papeda.
The citron is believed to be the purest of them all, since it is usually fertilized by self-pollination, and is therefore generally considered to be a male parent of any citrus hybrid rather than a female one.
Today, authorities agree that all citrus species are native to Southeast Asia where they are found wild and in an uncultivated form. The story of how they spread to the Mediterranean has been reported by Francesco Calabrese, Henri Chapot, Samuel Tolkowsky, Elizabetta Nicolisi, and others.
The citron could also be native to India where it borders on Burma, in valleys at the foot of the Himalayas, and in the Indian Western Ghats. It is thought that by the time of Theophrastus, the citron was mostly cultivated in the Persian Gulf on its way to the Mediterranean basin, where it was cultivated during the later centuries in different areas as described by Erich Isaac. Many mention the role of Alexander the Great and his armies as they attacked Persia and what is today Pakistan, as being responsible for the spread of the citron westward, reaching the European countries such as Macedonia and Italy.
The citron is mentioned in the Torah as being required for ritual use during the Feast of Tabernacles (Lev. 23:40). According to this tradition, the Jews brought it back to Israel from their exile in Egypt, where the Egyptologist and archaeologist Victor Loret claimed to have identified it depicted on the walls of the botanical garden at the Karnak Temple, which dates back to the time of Thutmosis III, approximately 3,000 years ago.
|“||In the east and south there are special plants... i.e. in Media and Persia there are many types of fruit, between them there is a fruit called Median or Persian Apple. The tree has a leaf similar to and almost identical with that of the andrachn (Arbutus andrachne L.), but has thorns like those of the apios (the wild pear, Pyrus amygdaliformis Vill.) or the firethorn, Cotoneaster pyracantha Spach.), except that they are white, smooth, sharp and strong.
The fruit is not eaten, but is very fragrant, as is also the leaf of the tree; and the fruit is put among clothes, it keeps them from being moth-eaten. It is also useful when one has drunk deadly poison, for when it is administered in wine; it upsets the stomach and brings up the poison. It is also useful to improve the breath, for if one boils the inner part of the fruit in a dish or squeezes it into the mouth in some other medium, it makes the breath more pleasant.
The seed is removed from the fruit and sown in the spring in carefully tilled beds, and it is watered every fourth or fifth day. As soon the plant is strong it is transplanted, also in the spring, to a soft, well watered site, where the soil is not very fine, for it prefers such places.
And it bears its fruit at all seasons, for when some have gathered, the flower of the others is on the tree and is ripening others. Of the flowers I have said those that have a sort of distaff [meaning the pistil] projecting from the middle are fertile, while those that do not have this are sterile. It is also sown, like date palms, in pots punctured with holes.
This tree, as has been remarked, grows in Media and Persia.
Pliny the Elder
|“||There is another tree also with the same name of "citrus," and bears a fruit that is held by some persons in particular dislike for its smell and remarkable bitterness; while, on the other hand, there are some who esteem it very highly. This tree is used as an ornament to houses; it requires, however, no further description.||”|
|“||The citron tree, called the Assyrian, and by some the Median apple, is an antidote against poisons. The leaf is similar to that of the arbute, except that it has small prickles running across it. As to the fruit, it is never eaten, but it is remarkable for its extremely powerful smell, which is the case, also, with the leaves; indeed, the odour is so strong, that it will penetrate clothes, when they are once impregnated with it, and hence it is very useful in repelling the attacks of noxious insects.
The tree bears fruit at all seasons of the year; while some is falling off, other fruit is ripening, and other, again, just bursting into birth. Various nations have attempted to naturalize this tree among them, for the sake of its medical properties, by planting it in pots of clay, with holes drilled in them, for the purpose of introducing the air to the roots; and I would here remark, once for all, that it is as well to remember that the best plan is to pack all slips of trees that have to be carried to any distance, as close together as they can possibly be placed. It has been found, however, that this tree will grow nowhere except in Media or Persia. It is this fruit, the pips of which, as we have already mentioned, the Parthian grandees employ in seasoning their ragouts, as being peculiarly conducive to the sweetening of the breath. We find no other tree very highly commended that is produced in Media.
|“||Citrons, either the pulp of them or the pips, are taken in wine as an antidote to poisons. A decoction of citrons, or the juice extracted from them, is used as a gargle to impart sweetness to the breath. The pips of this fruit are recommended for pregnant women to chew when affected with qualmishness. Citrons are good, also, for a weak stomach, but it is not easy to eat them except with vinegar.||”|
- Citron Cultivation, Production and Uses in the Mediterranean Region
- Cedrát - Citrus medica a Citrus limonimedica
- Theophrastus, Enquiry into Plants, IV.4.2.
- Citron at the Oxford English dictionary 
- Plant Lives
- Buddha's Hand citron by the University of California, Riverside
- Bangladeshi Shatkora Citrus: Candied Peel, Cordial, Posset & Pectin
- The Purdue University
- Natural healing Website
- National R&D Facility for Rasayana
- Citrus medica “Otroj”: Attenuates xidative Stress and Cardiac Dysrhythmia in Isoproterenol-Induced Cardiomyopathy in Rats
- Preparation and Characterization of Pectin...
- Researchers demonstrate how modified citrus pectin works against cancer
- See Etrog
- Un curieux Cedrat marocain, Chapot 1950.
- The citrus Industry, The Purdue University
- Citrus phylogeny and genetic origin of important species as investigated by molecular markers. 2000
- Assessing genetic diversity and population structure in a citrus germplasm collection utilizing simple sequence repeat markers (SSRs) by: Noelle A. Barkley, Mikeal L. Roose, Robert R. Krueger and Claire T. Federici
- Phylogenetic relationships in the “true citrus fruit trees” revealed by PCR-RFLP analysis of cpDNA. 2004
- The Search for the Authentic Citron: Historic and Genetic Analysis; HortScienc 40(7):1963–1968. 2005
- Chromosome Numbers in the Subfamily Aurantioideae with Special Reference to the Genus Citrus; C. A. Krug. Botanical Gazette, Vol. 104, No. 4 (Jun., 1943), pp. 602–611
- The relationships among lemons, limes and citron: a chromosomal comparison. by R. Carvalhoa, W.S. Soares Filhob, A.C. Brasileiro-Vidala, M. Guerraa.
- Calabrese, La favolosa storia degli agrumi. L'EPOS, 1998, Palerno Italy. English translation in Citrus: the genus citrus
- Capot, "The citrus plant", p.6-13. in: Citrus. Ciba-Geigy Agrochemicals Tech. Monogr.4. Ciba-Geigy Ltd., 1975, Basle, Switzerland.
- Tolkowsky, Hesperides. A history of the culture and use of citrus fruits, p.371. John Bale, Sons and Curnow, 1938, London, England.
- Nicolisi, Citrus Genetics, Breeding and Biotechnology
- The Citrus Industry ^The Purdue University ^Food in China: a cultural and historical inquiry By Frederick J. Simoons, Google Books ^The Search for the Authentic Citron: Historic and Genetic Analysis; HortScienc 40(7):1963–1968. 2005
- Sir Joseph Hooker. Flora of British India, i. 514)
- COUNTRY REPORT TO THE FAO INTERNATIONAL TECHNICAL CONFERENCE ON PLANT GENETIC RESOURCES (Leipzig, 1996); Prepared by: Nepal Agricultural Research Council; Kathmandu, June 1995; CHAPTER 2.2
- Isaac, "The Citron in the Mediterranean: a study in religious influences", Economic Geography, Vol. 35 No. 1. (Jan. 1959) pp. 71–78
- The Pordue University
- Journal of the Royal Horticultural Society
- THE INTRODUCTION OF CULTIVATED CITRUS TO EUROPE VIA NORTHERN AFRICA AND THE IBERIAN PENINSULA
- Historia plantarum 4.4.2-3 (exc. Athenaeus Deipnosophistae 3.83.d-f); cf. Vergil Georgics 2.126-135; Pliny Naturalis historia 12.15,16.
- Historia plantarum 1.13.4.
- Natural History Chp. 31
- Book XII CHAP. 7. (3.
- Chp. 56
- Citrus Fruits and Their Culture By H. Harold Hume
- All Kinds of Scented Wood By Richard S. Barnett
- Food in China: A Cultural and Historical Inquiry By Frederick J. Simoons
- Biology of Citrus By Pinhas Spiegel-Roy, Eliezer E. Goldschmidt
- The Encyclopaedia Britannica: “a” Dictionary of Arts, Sciences, Literature ... edited by Hugh Chisholm
- Citrus: The Genus Citrus By Giovanni Dugo, Angelo Di Giacomo
- The Encyclopædia Britannica: A Dictionary of Arts, Sciences, Literature and ... By Hugh Chisholm
- Fruit Breeding in India: Papers By G. S. Nijjar
- Proceedings, Google Book Search
- A Dictionary of Greek and Roman Culture
- International Standard Bible Encyclopedia: A-D By Geoffrey William Bromiley
- The Great Citrus Book: A Guide With Recipes By Allen Susser
- Citrus: The Genus Citrus By Giovanni Dugo, Angelo Di Giacomo - "Peel confection and candying"
- Penny Cyclopaedia of the Society for the Diffusion of Useful Knowledge
- Origin of Cultivated Plants By Alphonse de Candolle
- Evyatar Marienberg and David Carpenter, The Stealing of the ‘Apple of Eve’ from the 13th century Synagogue of Winchester, Henri III Fine Rolls Project, Fine of the Month: December 2011
|Wikispecies has information related to: Citrus medica|
- USDA Plants Profile - Citrus medica
- Purdue University (U.S.A.): article on citron culture and use.
- Citrus Pages
- University of California- "Citrus Diversity"
- Stuart-exchange_org:Citrus medica used as a medicinal plant.
- UCLA: "Give Me A Squeeze"
- Alchemy Works: Citron
- Wildflowers of Israel - Citron
- Differences between Lemon and Citron
- Buddha's Hand citron by David Karp (pomologist)