Taxonomic Classification of Citrus

Swingle’s Classification of Citrus (16 Species)

Genus: Citrus

Subgenus: Eucitrus

1. C. medica (Citron)

2. C. limon (Lemon)

3. C. aurantifolia (Lime)

4. C. aurantium (Sour Orange)

5. C. sinensis (Orange)

6. C. reticulata (Mandarin)

7. C. grandis (Pummelo)

8. C. paradisi (Grapefruit)

9. C indica (Indian Wild Orange)

10. C. tachibana (Tachibana Orange)

Subgenus: Papeda

11. C. ichangensis

12. C. latipes

13. C. micrantha

14. C. celebica

15. C. macroptera

16. C. hystrix

Under a revised classification, the only true species remaining in subgenus Eucitrus are:

1. C. medica (Citron)

2. C. reticulata (Mandarin)

3. C. grandis (Pummelo)

All other “species” are actually cultivated varieties, of hybrid origin, involving the above true species. For example.

C. sinensis (Orange) is believed to be a hybrid between C. reticulata X C. grandis with more genes coming from Mandarin than Pummelo.

C. limon (Lemon), a complex hybrid between C. medica with the lime, itself a hybrid.

C. aurantifolia – This may be a hybrid between C. medica with a species in the subgenus Papeda. It has also been suggested there may be (micro)citrus parentage involved, due to the small flowers and leathery, thin skinned fruit, but this is unproven.

C. aurantium (Sour Orange) is a similar hybrid to the sweet orange, but it is speculated that another type of mandarin was involved in the parentage, to explain the morphological differences between it and Sweet Orange.

C. paradisi is a hybrid between Pummelo and Sweet Orange, which occurred in the Carribean Islands in the early 1800’s.

C indica and C. tachibana are believed to be natural hybrids of the above true species.

However, Eremocitrus and Microcitrus have been recently reclassified back into the genus citrus, so including these citrus species, the total number of true citrus species is 10.