Citrus (idea)

domain Eucarya
kingdom Plantae
division Magnoliophyta (formerly Phylum Tracheophyta)
class Magnoliopsida (formerly Class Angiospermae)
superorder Rosidae or Rutiflorae
order Sapindales or Rutales
family Rutaceae
subfamily Aurantioidiae
tribe Citreae
subtribe Citrinae
genus Citrus

A genus of tropical plants, many of which produce fruits of vast commercial importance.

A variety of some Citrus plant probably developed in the Indonesian Archipelago some 20 million years ago.  It probably had bitter fruit.  Some time during man's wanderings into the area before the last Ice Age, this plant was discovered, and its juice was used for medicinal purposes.   At some point, these plants were cultivated in India and/or China, from which the sweet varieties were developed.  Today, they are cultivated wherever the climate allows, often augmented by irrigation.

There are two subgenera of Citrus: one also called Citrus, and the other called Papeda.   All commercial citrus comes from the first subgenus.  The fruits are the familiar sections of numerous juicy capsules with papery coverings, arranged radially around the axis of the fruit, with a fleshy covering and a waxy exterior. All Citrus leaves are obovate with a point at the tip (spearpoint-shaped).  Most Papeda plants have bitter, inedible fruits; they can be recognized by leaves which grow along the stems and interconnect with each other.  It is difficult to tell which Citrus are wild and which are cultivated; most 'wild' species are probably in the Papeda group.

Any attempt to state the number of actual Citrus species would be pointless.  Due to its long history of being cultivated, the  several species of the Citrus subgenus are all cross-fertile, and produce fertile offspring.  Indeed, Citrus plants can crossbreed with members of Fortunella (kumquat).   We have no idea how many hybrids were produced in the past; even worse, it is in the interest of commercial growers to have their specialized cultivars recognized as distinct species.  Furthermore, naitonal pride appears to figure into the mix.

Not surprisingly, the classification of various Citrus plants into species is highly controversial.  In 1875, Joseph D. Hooker recognized just four Citrus species.  Walter T. Swingle, in 1943, identified 15 species.  in 1954, Dr. Takesi Tanaka, using looser criteria to distinguish one species from another, recognized 145!

In the list below:

• Members of subgenus Citrus are marked with a (C), members of Papeda are marked with a (P).
• Very Large, bold names are commerically important species.
• Tanaka species appear indented under the Swingle species they are associated with.
• I'm not sure about the associations of some species, these are marked with a (?)
• I've taken the liberty of merging C. paradisi into C. maxima as many sources do this, even though EGID does not.

• C. aurantifolia (C)  (lime)
  • subsumes C. latifolia
  • subsumes C. davoensis  (P) (Dawao lemon)
  • subsumes C. excelsa  (P)
  • subsumes C. hyalopulpa
  • subsumes C. javanica
  • subsumes C. latifolia
  • subsumes C. limettoides
  • subsumes C. longispina  (P)
  • subsumes C. montana
  • subsumes C. macrophylla  (P)
  • subsumes C. obversa
  • subsumes C. ovata
  • subsumes C. papaya
  • subsumes C. pennivesiculata
  • subsumes C. webberi (P)
• C. aurantium (C) (sour or bitter orange, Seville Orange)
  • subsumes C. bergamia (Bergamot)
  • subsumes C. bigaradia (Bigarde Orange)
  • subsumes C. vulgaris
  • subsumes C. canaliculata
  • subsumes C. maderaspatama
  • subsumes C. myrtifolia
  • subsumes C. neoaurantium
  • hybrid: C. pappilaris
  • subsumes C. rokugatsu
  • subsumes C. taiwanica
  • subsumes C. yanbaruensis
• C. celebica
• C. halimii  (new)
• C. hystrix  (P) (Thai lime, kaffir lime)
• C. ichangensis (P) (Ichang lemon, Papeda, yuzu)
  • Hybrid: C. hanaju
  • subsumes C. junos  (P) (yuzu)
  • subsumes C. sudachi  (P)
  • subsumes C. takuma-sudachi
  • subsumes C. wilsonii
• C. kizu  (?)
• C. latipes  (P)
• C. limon (C) (lemon)
  • subsumes C. assamensis
  • subsumes C. balotina
  • subsumes C. duttae
  • subsumes C. jambhiri (rough lemon, citronelle)
  • subsumes C. karna
  • subsumes C. limetta
  • subsumes C. limonia (Mandarin lime, Canton lemon, Khatta orange, Rangpur lime)
  • subsumes C. longilimon
  • subsumes C. lumia
  • subsumes C. macrolimon
  • subsumes C. megaloxycarpa
  • subsumes C. meyerii
  • subsumes C. pyrifomis (Yellow Wonder)
  • subsumes C. rissoi
  • subsumes C. sarbati
• C. limonum (small Egyptian lime)  (?)
• C. luminciana  (?)
• C. macroptera  (P)
• subsumes C. combara
• subsumes C. kerni
• C. maxima (C)  (shaddock, pomelo, grapefruit)
  • subsumes C. ampullacea
  • subsumes C. asahikan
  • subsumes C. aurantiacia
  • subsumes C. decumana
  • subsumes C. flavicarpa
  • subsumes C. glaberrima (Silk-skinned orange, kinukawa)
  • subsumes C. grandis
  • subsumes C. hassaku
  • subsumes C. intermedia
  • subsumes C. iwaikan
  • subsumes C. kotokan
  • subsumes C. medioglobosa
  • subsumes C. miaray
  • subsumes C. mistuharu
  • subsumes C. natsudaidai
  • subsumes C. panuban
  • subsumes C. paradisi
  • subsumes C. pseudogulgul
  • subsumes C. obovoidea
  • subsumes C. ornikanto
  • subsumes C. otachibana
  • subsumes C. rugulosa
  • subsumes C. sulcata
  • subsumes C. tengu
  • subsumes C. tosa-asahi
  • subsumes C. truncata
  • subsumes C. yamabuki
  • subsumes C. yuge-hyokan
• C. medica (C)  (citron)
  • subsumes C. limonimedica
  • subsumes C. nana
  • subsumes C. odorata
• C. micrantha
• C. reticulata(C) (clementine, mandarin orange, satsuma, tangerine)
  • subsumes C. amblycarpa (nasnaran)
  • subsumes C. benikoji
  • subsumes C. chuana
  • subsumes C. clementina (clementine)
  • subsumes C. cleopatra  (?)
  • subsumes C. crenatifolia
  • subsumes C. deliciosa
  • hybrid: C. depressa  (voangasay, Flat or Hirami Lemon)
  • subsumes C. erythrosa
  • subsumes C. genshokan
  • hybrid: C. inflata
  • subsumes C. keraji
  • subsumes C. limonellis
  • subsumes C. madurensis (P)
    • subsumes C. microcarpa
    • subsumes C. mitis
  • hybrid: C. nippokoreana
  • hybrid: C. nobilis (King Orange)
  • hybrid: C. oto
  • subsumes C. paratangerina
  • subsumes C. platymamma
  • hybrid: C. pseudoaurantium
  • subsumes C. reshni (Cleopatra)
  • subsumes C. suavissima
  • subsumes C. unshiu
  • subsumes C. succosa
  • subsumes C. suhiensis
  • subsumes C. sunki
  • subsumes C. tangerini
  • subsumes C. tardiferax
  • subsumes C. tardiva
  • hybrid: C. tarogayo
  • hybrid: C. tumida
  • hybrid: C. yatsushiro
  • hybrid: C. yuko
• C. rocarpa (Kabosu)  (?)
• C. siniensis (C) (sweet oranges: Blood Orange, Navel Orange, Valencia)
  • subsumes C. aurea
  • subsumes C. funadoko
  • subsumes C. iyo
  • subsumes C. luteo-turgida
  • subsumes C. oblonga
  • subsumes C. shunokan
  • subsumes C. sinograndis
  • subsumes C. tamurana
  • subsumes C. tankan
  • subsumes C. temple (Temple Orange mmmm....)
  • subsumes C. ujukitsu
• C. sphaerocarpa (?)
• C. tachibana
  • subsumes C. erythrosa
  • subsumes C. kinokuni
  • subsumes C. oleocarpa
  • subsumes C. ponki

"Survey of Phenolic Compounds Produced in Citrus", Appendix 2
Mark Berhow, Brent Tisserat, Katherine Kanes, and Carl Vandercook
United States Department of Agriculture
Agricultural Research Service
http://www.ars.usda.gov/is/np/phenolics/title.htm

Citrus Variety Collection
University of California, Riverside
http://cnas.ucr.edu/~citrus/

Sorting citrus names
http://gmr.landfood.unimelb.edu.au/Plantnames/Sorting/Citrus.html

EGID-Citrus Network
Citrinae Subtribe classification, January 2001
http://www.corse.inra.fr/sra/species.pdf

The primary classification sources appear to be:

Hooker, JD. Flora of British India. Rutaceae, 1:484-517.  Reeve and Co, London, 1875.

Swingle, WT. "The botany of citrus and its wild relatives of the orange subfamily". Pp. 129-474 in:HJ Webber and LD Batchelor, eds. The Citrus Industry. Vol i. History, Botany, and Breeding. Univ of California Press, Berkeley,  1943.

Tanaka, T. Species problems in Citrus. Japanese Society for the Promotion of Science, Tokyo, 1954.