Citrus medica L. (Rutaceae)

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Citron


Citron, with its probable northern Indian origin, is known for its enormous, aromatic, thick-skinned fruit. The first scientific description of the citron in western literature was by the Greek philosopher Theophrastus, the 'father of botany', in the third century BC. Besides portraying the fruit, Theophrastus wrote the first description of the female reproductive parts of a flower and described floral monoecy (separate male and female flowers on the same plant): 'in the citron those flowers which have a kind of distaff growing in the middle are fruitful, but those that have it not are sterile'. Four centuries later, Pliny wrote about Roman uses of citron, especially in medicine, although most of his information was taken from Theophrastus.

Citron fruits have very little juice but their thick, oil-rich skins are important for the production of candied peel and for flavouring and scent. Furthermore, the fruit is used in some religious rituals. As might be expected, after two millennia of selection for different purposes, by multiple human cultures, numerous citron varieties have been produced, of which one of the most bizarre is the octopus-like fruit known as 'Buddha's Hand'.

Citrus medica is a small, evergreen, spiny tree that tested the skills of northern European gardeners interested in growing horticultural curiosities. Pliny observed citron could not be cultivated successfully in Roman Italy. By the seventeenth century, oranges and their relatives were symbols of status and power, and became highly desirable European horticultural plants. However, the glasshouses and stoves of the time lacked precise temperature control and clean heating systems. Jacob Bobart the Elder failed to sustain 'Malus Medica' or 'pomecitron tree' in the 1648 Botanic Garden's stove; by 1658 it was absent from the collection.

'Malus Medica' is usually equated with citron but in Bobart's time the subtle distinctions among citron, lemon (Citrus x limon) and lime (Citrus x aurantiifolia) were hardly recognised. Consequently, without herbarium specimens, it is impossible to know which specific fruit was being grown in the Garden. We now know lemons and limes are ancient interspecific hybrids, with citron in their respective ancestries.

Carolus Linnaeus's use of 'medica' in the species epithet does not refer to citron's medicinal use but rather its association with the classical empires of Persia and Media. In classical stories, some researchers have argued citron is the Golden Apples of the Hesperides and the fruit of the Tree of Knowledge in the Garden of Eden.

Further reading

Calabrese F 2002. Origin and history. In: Dugo G and di Giacomo A (eds) Citrus. The genus Citrus. Taylor & Francis, pp. 1-15.

Ramón-Laca L 2003. The introduction of cultivated citrus to Europe via northern Africa and the Iberian Peninsula. Economic Botany 57, 502-514.

Stephen Harris

BBC Radio Oxford clip about this week's plant