Citrus aurantium

An evergreen tree reaching 9 m tall by 6 m wide, growing at a medium rate. Hardy to UK zone 9 and frost tender. In leaf year-round with flowers from April to June. Hermaphroditic and self-fertile, pollinated apomictically and by insects. Noted for attracting wildlife. Grows in medium loamy and heavy clay soils, preferring well-drained conditions. Suitable for mildly acid and neutral soils, tolerating very alkaline soils. Requires full sun and prefers moist soil.

Description

An evergreen tree up to 10-15 m high and with slender thorns. It spreads to 5 m across. The stem is stout and erect. It is covered with smooth greyish-brown bark. The leaf stalks have broad wings. The leaves are glossy green, oval and 10 cm long. The leaves taper towards the base and are paler under the leaf. There are spines in the axils of the leaves. The flowers are white and have a sweet smell. They are 2 cm across and there can be 1, 2 or a cluster, in the axils of leaves. The fruit is often green with a reddish tinge and fairly juicy but sour. The fruit are 5-7 cm long. The fruit is often rough skinned. The flesh is divided into segments with sour pulp.

Edible Uses

The fruit is very bitter and is mainly used in making marmalade and other preserves; it measures approximately 5–7cm in diameter. The rind is used as a flavouring in cakes and as an ingredient in bouquet garni. An oil from the seeds contains linolenic acid and is increasingly used as a food due to its ability to reduce blood cholesterol levels. The flowers are used to scent tea. An essential oil from the dried peel of immature fruits is used as a food flavouring.

Traditional Uses

The fruit is bitter, therefore mostly used for marmalade or flavouring. The fruit are used for peel and for sherry and wine. The tree is used as a rootstock for budding or grafting other citrus on to. The oil from the flowers is used for flavouring. The flowers are used for flavouring tea. Immature fruit are pickled in salt or vinegar or fried in coconut oil.

Medicinal Uses

Citrus species contain a wide range of active ingredients, including vitamin C, flavonoids, acids, and volatile oils, and research into their uses is ongoing. They also contain coumarins such as bergapten, which sensitizes the skin to sunlight and is sometimes added to tanning preparations to promote pigmentation, though it can cause dermatitis or allergic reactions in some people. The plants contain umbelliferone, which is antifungal, as well as antibacterial and antifungal essential oils, and the pyrone citrantin, which shows antifertility activity and was once used in contraceptives. Both leaves and flowers are antispasmodic, digestive, and sedative; an infusion treats stomach problems and sluggish digestion. The fruit is antiemetic, antitussive, carminative, diaphoretic, digestive, and expectorant — used either immature (Zhi Shi) or mature with seeds and endocarp removed (Zhi Ke), with the immature fruit having the stronger action. These preparations treat dyspepsia, constipation, abdominal distension, stuffy sensation in the chest, and prolapse of the uterus, rectum, or stomach. The fruit peel is bitter, digestive, and stomachic. Seeds and pericarp treat anorexia, chest pains, colds, and coughs. The essential oil is used in aromatherapy for depression, tension, and skin problems, with the keyword 'Radiance'.

Distribution

A tropical and subtropical plant. Mostly in coastal areas in the tropics. It is drought and frost resistant. It does best in a protected sunny position. It must have a temperature above 3-5°C to grow. It suits hardiness zones 9-11.

Where It Grows

Africa, Argentina, Asia, Australia, Balkans, Bangladesh, Belize, Brazil, British Indian Ocean Terr., BIOT, Burkina Faso, Cambodia, Cameroon, Central Africa, Central America, China, Colombia, Congo DR, Costa Rica, Croatia, Cuba, East Africa, Ecuador, Ethiopia, Europe, Fiji, France, Grenada, Guam, Guatemala, Guyana, Haiti, Hawaii, Himalayas, India, Indochina, Indonesia, Italy, Japan, Kenya, Laos, Madagascar, Malawi, Malaysia, Maldives, Marquesas, Mediterranean, Mexico, Micronesia, Middle East, Morocco, Mozambique, Myanmar, Nepal, New Caledonia, Nicaragua, North Africa, North America, Northeastern India, Pacific, Pakistan, Papua New Guinea, PNG, Paraguay, Peru, Philippines, Puerto Rico, Samoa, Sao Tome and Principe, Saudi Arabia, SE Asia, Senegal, Sierra Leone, Slovenia, Solomon Islands, South Africa, Southern Africa, South America, Spain, Sri Lanka, Suriname, Tanzania, Thailand, Taiwan, Tokelau, Tonga, Trinidad, Turkey, Türkiye, USA, Vanuatu, Vietnam*, West Africa, West Indies, Zimbabwe,

Cultivation

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. Most Citrus species are self-fertile, meaning they can produce fruit without needing another plant for cross-pollination, though cross-pollination can improve fruit set in some varieties. Citrus fruits are generally harvested in late autumn to early spring, depending on the specific variety and local climate. Citrus trees usually flower in the spring. Some species may have a second flowering period in late summer.

Propagation

Sow fresh seed in a greenhouse after thoroughly rinsing. Sow stored seed in March in a greenhouse. Germination usually takes place within 2–3 weeks at 13°C. Seedlings are prone to damping off and must be watered carefully and kept well ventilated. Seed is usually polyembryonic — two or more seedlings arise from each seed, genetically identical to the parent and typically free of any virus present in the parent. Prick out into individual pots when large enough to handle and grow on in the greenhouse for at least three growing seasons before attempting to establish outdoors. Plant out in summer with cold protection for the first few winters. Half-ripe cuttings can be taken in July–August in a frame. Layering in October.

Other Uses

This species is widely used as a rootstock for sweet orange (C. sinensis) due to its disease resistance and greater hardiness. It is also grown as a hedging plant in North America. A semi-drying oil from the seed is used in soap making. Essential oils from the peel, petals, and leaves are used as food flavourings and in perfumery and medicines. The flower oil, called neroli oil, is produced in very low yields from this species and is often adulterated with inferior oils. The oil from leaves and young shoots, called petit-grain, requires around 400 kilos of plant material to yield approximately 1 kilo of oil and is also frequently adulterated. Neroli oil mixed with vaseline is used in India as a preventative against leeches.

Other Information

Trees are scattered in a number of coastal areas in Papua New Guinea but fruit are not used and just left lying under the tree. It is cultivated.

Notes

This plant is mostly used as rootstock for other citrus. There are 20 Citrus species. Several hybrids have been formed.

Nutrition

Synonyms

Also Known As

Apepu, Arancio amaro, Bigarade, Bitter orange, Daidai, Embul-dodan, Gwanggyul, Heralay, Jeruk manis, Kabala, Kadarai, Karna, Khatta, Laoranjy, Laranja-azeda, Laranja-cavalo, Laranja-pocan, Ljuta naranca, Mallikanarangi, Moli jamu, Moli kula, Mshuza, Naaringu, Nandam, Narang, Narangam, Naranja amargo, Naranjo agrio, Narattai, Satkora, Sour orange, Suan cheng, Taitai, Turunc, Voangdy, Zure oranjes

References (90)

• AAK, 1980, Bertanam Pohon Buah-buahan. Penerbitan Yayasan Kanisius, Jogyakarta. p 29
• AAK, 1994, Jeruk, Penerbit Kanisius, Jogyakarta. p 189
• Ambasta, S.P. (Ed.), 2000, The Useful Plants of India. CSIR India. p 128
• Amin, M. et al, 2023, Edible wild plant species used by different linguistic groups of Kohistan Upper Khyber Pakhtunkhwa (KP), Pakistan. Journal of Ethnobiology and Ethnomedicine 19:6 p 8
• Barwick, M., 2004, Tropical and Subtropical Trees. A Worldwide Encyclopedic Guide. Thames and Hudson p 117

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