Citrus sinensis

green oranges


Citrus sinensis

(L.) Osbeck 1765

pronounced: SIT-russ sy-NEN-siss

(Rutaceae — the lemon family)


common name: orange

Citrus is the ancient Latin name for the citrus tree; sinensis is late Latin (16th century) for ‘Chinese’. The word orange comes from a transliteration of the Sanskrit word naranga, which comes from the Tamil naru (fragrant).

The orange is a hybrid of ancient cultivated origin, possibly between the pomelo (Citrus maxima) and the tangerine (Citrus reticulata). It is a small flowering tree growing to about 10 m tall with glossy evergreen leaves, arranged alternately, of oval shape with crenulate margins and 4–10 cm long.

The fragrant white flower has 5 petals and bright yellow stamens. Orange blossom is traditionally associated with good luck, and has long been popular in bridal bouquets.

The orange fruit is an hesperidium, a type of berry, deriving as it does from a single ovary. It has a thick bitter rind that is usually discarded, but can be used in some recipes as a flavouring or a garnish. The outermost layer of the rind can be grated to produce orange zest. This zest is popular in cooking because it contains the oil glands and has a strong flavour similar to the fleshy inner part of the orange. The white part of the rind, called the pericarp or albedo, and including the pith, is a source of pectin and has nearly the same amount of vitamin C as the flesh.

Oranges originated in south-east Asia. All citrus trees are of the single genus Citrus, and remain largely interbreedable; i.e., there is only one ‘superspecies’ which includes grapefruits, lemons, limes and oranges. Nevertheless, names have been given to various members of the genus. Besides Citrus sinensis, the sweet orange, there is also Citrus aurantium, the bitter orange.

The navel orange has an interesting history. It originated in a single mutation in 1820 in an orchard of sweet oranges planted at a monastery in Brazil. The mutation caused the orange to develop a second smaller orange at the base of the original fruit, as a conjoined twin with a set of smaller segments embedded within the peel of the larger orange. From the outside, it looks rather like the human navel, hence its name. Because the mutation left the fruit seedless, and therefore sterile, the only means available to cultivate more of this new variety was to graft cuttings on to other varieties of citrus tree. Two such cuttings of the original tree were transplanted to Riverside, California, in 1870, and this eventually led to worldwide popularity. Today, navel oranges continue to be produced by cutting and grafting. This does not allow for the usual selective breeding methodologies, and so, not only do the navel oranges of today have exactly the same genetic makeup as the original tree, and are therefore clones, but also all navel oranges can be considered to be the fruit of that single, almost 200-year-old tree.

Like all citrus fruits, the orange is acidic, with a pH level of around 2.5–3, depending on the age, size and variety of the fruit. Although this is not as acidic, generally speaking, as the lemon, it is still quite strong on the pH scale – as strong as vinegar or citric acid.

The orange tree is a great favourite with moth and butterfly larvae, including:
       • the Emperor Moth Syntherata janetta;
       • the Carob Moth Ectomyelois ceratoniae;
       • the Light Brown Apple Moth Epiphyas postvittana;
       • the Orange Fruit Borer Isotenes miserana;
       • the Pecan Stem Girdler Maroga melanostigma;
       • the Wattle Cup Caterpillar Calcarifera ordinata;
       • the Dainty Swallowtail Papilio anactus;
       • the Fuscous Swallowtail Papilio fuscus; and
       • the Citrus Flower Moth Prays nephelomima.

The timber is yellowish, hard and fine-grained. It is used in inlaid work, turning and carving. If a tree is large enough to produce a millable log, the wood can be used for furniture and panelling.


Photographs taken in Picnic Bay 2009, 2012
Page last updated 10th November 2018