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Common Name: Bitter Orange

General Information

Citrus aurantium is an evergreen tree that can grow up to 9.00 metres tall.
It is harvested from the wild for local use as a food, medicine and source of materials.

Known Hazards

None known

Botanical References

Range

Tropical Asia?

Habitat

Original habitat is obscure, possibly a back cross involving C. maxima X C. reticulata[].

Properties

Edibility Rating
Medicinal Rating
Habit	Evergreen Tree
Height	9.00 m
Pollinators	Apomictic, Insects
Self-fertile	Yes
Cultivation Status	Wild

Cultivation Details

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 4.8 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[].
Dormant plants can withstand temperatures down to about -6°c so long as this is preceded by cool weather in order to harden off the plant[]. The young growth in spring, even on mature plants, is frost-tender and so it is best to grow the plants in a position sheltered from the early morning sun[]. A tree grown outdoors on the coast at Salcombe in Devon lived for over 200 years[].
The bitter orange is often grown for its edible fruit in warm temperate and tropical zones, there are many named varieties[]. In Britain it can be grown in a pot that is placed outdoors in the summer and brought into a greenhouse during the winter[, ].
Plants dislike root disturbance and so should be placed into their permanent positions when young. If growing them in pots, great care must be exercised when potting them on into larger containers[].

Edible Uses

Fruit - raw or cooked[, ]. Very bitter[]. It is used in making marmalade and other preserves[, , , ]. The fruit is about 5 - 7cm in diameter[].
The rind of the fruit is often used as a flavouring in cakes etc[, ]. Used in 'bouquet garni'[].
An oil obtained from the seeds contains linolenic acid and is becoming more widely used as a food because of its ability to reduce levels of cholesterol in the blood[].
The flowers are used for scenting tea[].
An essential oil from the dried peel of immature fruits is used as a food flavouring[].

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 plants also contain umbelliferone, which is antifungal, as well as essential oils that are antifungal and antibacterial[]. They also contain the pyrone citrantin, which shows antifertility activity and was once used as a component of contraceptives[].
Both the leaves and the flowers are antispasmodic, digestive and sedative[, ]. An infusion is used in the treatment of stomach problems, sluggish digestion etc[].
The fruit is antiemetic, antitussive, carminative, diaphoretic, digestive and expectorant[].The immature fruit can be used (called Zhi Shi in China) or the mature fruit with seeds and endocarp removed (called Zhi Ke). The immature fruit has a stronger action. They are used in the treatment of dyspepsia, constipation, abdominal distension, stuffy sensation in the chest, prolapse of the uterus, rectum and stomach[].
The fruit peel is bitter, digestive and stomachic[].
The seed and the pericarp are used in the treatment of anorexia, chest pains, colds, coughs etc[].
The essential oil is used in aromatherapy. Its keyword is 'Radiance'[]. It is used in treating depression, tension and skin problems[].

Other Uses

This species is much used as a rootstock for the sweet orange, C. sinensis, because of its disease resistance and greater hardiness[, , ].
Grown as a hedging plant in N. America[].
A semi-drying oil obtained from the seed is used in soap making[, ].
Essential oils obtained from the peel, petals and leaves are used as a food flavouring and also in perfumery and medicines[, , , , ]. The oil from the flowers is called 'Neroli oil' - yields are very low from this species and so it is often adulterated with inferior oils[]. The oil from the leaves and young shoots is called 'petit-grain' - 400 kilos of plant material yield about 1 kilo of oil[]. This is also often adulterated with inferior products[].
Neroli oil, mixed with vaseline, is used in India as a preventative against leeches[].

Propagation

The seed is best sown in a greenhouse as soon as it ripe after thoroughly rinsing it[, ]. Sow stored seed in early spring in a greenhouse[]. 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 polyembrionic, 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 in the greenhouse for at least three growing seasons before trying them outdoors. Plant them out in the summer and give them some protection from the cold for their first few winters outdoors.
Cuttings of half-ripe wood, mid summer in a frame.
Layering in early autumn.