Common Name: Sweet Orange

General Information

Citrus sinensis is a small, shallow-rooted evergreen shrub or tree growing about 6 - 13 metres tall with an enclosed conical top and mostly spiny branches[].
A very well known fruit, widely available in countries around the world. The tree is commonly cultivated for its fruit in warm temperate, subtropical and tropical zones[]. It prefers a prominent change in the seasons and so is not so suited to the tropics, where it is grown more as a garden tree, but is widely grown commercially in the subtropics[].

Known Hazards

None known

Botanical References

Range

Original range is obscure, possible Asia in southern China and Vietnam.

Habitat

Original habitat is obscure, possibly an introgressed hybrid of C. maxima x C. reticulata[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	9.00 m
Growth Rate	Medium
Pollinators	Apomictic, Insects
Self-fertile	Yes
Cultivation Status	Cultivated

Cultivation Details

A shallow rooted plant[], it prefers a deep, well-drained but moisture-retentive loamy soil in full sun[]. Trees are intolerant of waterlogging[]. Prefers a pH in the range 5 - 6[].
Prefers a moderately heavy loam with a generous amount of compost and sand added and a very sunny position[, ]. Prefers a pH between 5 and 6[]. Tolerates a pH in the range 4.3 to 8.3. Plants are intolerant of water logging[]. When growing plants in pots, a compost comprising equal quantities of loam and leafmould plus a little charcoal should produce good results[]. Do not use manure since Citrus species dislike it[]. When watering pot plants it is important to neither overwater or underwater since the plant will soon complain by turning yellow and dying. Water only when the compost is almost dry, but do not allow it to become completely dry[].
Three main climates are suitable for commercial citrus production - tropical climates, subtropical with winter rain such as in the Mediterranean and semitropical with summer rainfall as found in Florida and southern Brazil[]. The optimal temperatures for citrus cultivation range between 25 - 30°c, with the coldest month having an average minimum of at least 15°c[]. Growth generally ceases below 13°c and above 38°c[]. If there are dry periods of more than three months, then irrigation will be necessary[].
The flowers are sweetly scented[].
Plants dislike root disturbance and so should be placed into their permanent positions when young[].
The sweet orange is not known anywhere as a wild plant but must have originated near the border between China and Vietnam[].
Sweet orange starts flowering and bearing fruit after 3-5 years[]. Trees aged 3-4 years produce 2.5-5 t/ha of fruit and 8-12 year old trees produce 20-40 t/ha of fruit. Single trees may live up to 100 years, but the economic life of an orchard seldom exceeds 30 years[].
There are many named varieties[].

Edible Uses

Fruit - raw. Sweet, juicy and delicious[, , , ]. The juice is often extracted from the fruit and sold as a refreshing and healthy drink or used in jellies, ice cream etc[]. The dried and pulverized fruits are used for flavouring baked goods[]. The orange, reddish-green to yellowish-green fruit is round and 4 - 12cm in diameter[]. A good source of vitamin C[].

The essential oil extracted from the peel of the fruits is used for flavouring drinks, ice-cream, pudding, desserts, chewing gum, and sweetmeats[].

Pectin, a setting agent, is made from the peel[].

The rind of the fruit is often candied and used as a flavouring in cakes etc or made into marmalade[, , , ].

Flowers - cooked as a vegetable or made into a tea[].

An oil extracted from the seeds is used as a cooking oil[].

Medicinal

Citrus species contain a wide range of active ingredients and research is still underway in finding uses for them. They are rich in vitamin C, flavonoids, acids and volatile oils. They also contain coumarins such as bergapten which sensitizes the skin to sunlight. Bergapten is sometimes added to tanning preparations since it promotes pigmentation in the skin, though it can cause dermatitis or allergic responses in some people[]. Some of the plants more recent applications are as sources of anti-oxidants and chemical exfoliants in specialized cosmetics[].

The fruit is appetizer and blood purifier[]. It is used to allay thirst in people with fevers and also treats catarrh[].

The fruit juice is useful in the treatment of bilious affections and bilious diarrhoea[].

The fruit rind is carminative and tonic[]. The fresh rind is rubbed on the face as a cure for acne[].

The dried peel is used in the treatment of anorexia, colds, coughs etc[].

A decoction of the leaves with salt is taken orally for digestive tract ailments, nerve disorders, fever, asthma, blood pressure, general fatigue and vomiting[].

The crushed leaves or fruit juice is massaged into the skin to relieve itching[]. Fruit juice or leaf decoction with sugar is taken orally for cold and loss of appetite, while crushed leaf decoction as a bath relieves headache and rheumatism[].

Macerated root, leaf or fruit mesoderm is taken orally for urethritis[]. Macerated fruit mesoderm or bark decoction is taken orally for liver ailments[]. Broken bones are massaged with roasted fruit[].

Leaf oil exhibits carminative properties and light antispasmodic and sedative properties[].

Other Uses

A semi-drying oil obtained from the seed is used in soap making[, ].

An essential oil from the peel is used as a food flavouring and also in perfumery and medicines[, , ].
The leaves and flowers also contain fine essences of oils that may be used in the manufacture of cosmetics[].

A potential source of firewood[].

The wood can be used for boards and panelling[].

Propagation

The seed is best sown in containers as soon as it is ripe, after thoroughly rinsing it[, ]. Sow stored seed in containers as soon as possible]. Germination usually takes place within 2 - 3 weeks at 13°c. Seedlings are liable to damp off so they must be watered with care and kept well ventilated. The seed is usually polyembryonic, two or more seedlings arise from each seed and they are genetically identical to the parent but they do not usually carry any virus that might be present in the parent plant[]. When large enough to handle, prick the seedlings out into individual pots and grow them on until they are 10cm or more tall before planting out into their permanent positions.
Cuttings of half-ripe wood, July/August in a frame. This species grows easily from cuttings[].
Layering in October.

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