Citrus sinensis

Evergreen tree reaching 9m tall, growing at a medium rate. Hardy to UK zone 9 but frost tender. Self-fertile with hermaphroditic flowers pollinated by insects and apomictic reproduction. Year-round foliage attracts wildlife. Requires full sun and well-drained soil; tolerates mildly acid to mildly alkaline conditions and can grow in very acid or very alkaline soils. Prefers moist soil and grows in loamy or clay soils.

Description

An evergreen tree up to 8-10 m high. It spreads to 4 m across. The stem is short, stout and spiny. It has a dense, rounded crown. The leaves are dark green, sword shaped and tapering towards the tip. They are 5-15 cm long. The leaves have a sweet smell when crushed. The leaf stalks have narrow wings and the stalk is jointed to the blade. The flowers are white and have a scent. The flowers have 5 petals and occur either singly or in clusters. The fruit often remain green colour and don't turn orange when ripened below 600 m altitude in the tropics. The fruit are about 9 cm across. They have 10-14 segments.

Edible Uses

The fruit is eaten raw — sweet and delicious. The juice is widely extracted for use as a refreshing drink or in jellies and ice cream. The rind is used as a flavouring in cakes and similar baked goods, or made into marmalade. The flowers can be cooked as a vegetable or brewed into a tea.

Traditional Uses

The fruit is eaten fresh, and the juice used in drinks. They are also added to salads and made into wine. The juice is canned, bottled, and used in ice cream and jellies. The peel is candied and used for flavouring. It is made into marmalade. The flower petals are eaten as a vegetable. The roots are used to flavour soup.

Medicinal Uses

Citrus species contain a wide range of active compounds, and research into their applications is ongoing. They are rich in vitamin C, flavonoids, acids, and volatile oils, and also contain coumarins such as bergapten, which sensitizes the skin to sunlight. Bergapten is sometimes added to tanning preparations to promote skin pigmentation, though it can cause dermatitis or allergic reactions in some people. Recent applications include use as sources of antioxidants and chemical exfoliants in specialized cosmetics. The fruit acts as an appetizer and blood purifier, allays thirst in people with fevers, and treats catarrh. The fruit juice is useful in treating bilious affections and bilious diarrhoea. The rind is carminative and tonic; the fresh rind can be rubbed on the face as a treatment for acne, while the dried peel is used for anorexia, colds, and coughs.

Distribution

A subtropical plant. Not suited to very wet areas. Not suited to high altitudes. In PNG it grows between sea levels and 1,800 m above sea level. Seeds won't grow below 13 °C. They need a well drained, fertile, sandy soil. They are drought and frost tender. Trees need temperatures above 3-5°C to grow. In Brisbane Botanical Gardens. It suits hardiness zones 9-11.

Where It Grows

Africa, Algeria, Andes, Angola, Argentina, Asia, Australia, Bangladesh, Barbados, Benin, Bhutan, Bougainville, Brazil, Cambodia, Cameroon, Caucasus, Central Africa, Central African Republic, CAR, Central America, Central Asia, China*, Colombia, Congo DR, Cook Islands, Costa Rica, Cuba, Dominican Republic, East Africa, East Timor, Ecuador, Egypt, Ethiopia, Europe, Fiji, French Guiana, Georgia, Ghana, Grenada, Guam, Guianas, Guinea-Bissau, Guyana, Haiti, Hawaii, Himalayas, Europe, India, Indochina, Indonesia, Italy, Jamaica, Japan, Kenya, Kiribati, Korea, Laos, Madagascar, Malawi, Malaysia, Malta, Marquesas, Mauritania, Mediterranean, Mexico, Micronesia, Middle East, Morocco, Mozambique, Myanmar, Nauru, Nepal, Nicaragua, Niger, Nigeria, North Africa, North America, Northeastern India, Pacific, Pakistan, Palau, Panama, Papua New Guinea, PNG, Peru, Philippines, Portugal, Rotuma, Sahel, Samoa, Sao Tome and Principe, Saudi Arabia, SE Asia, Senegal, Sierra Leone, Solomon Islands, South Africa, Southern Africa, South America, Spain, Sri Lanka, Suriname, Taiwan, Tajikistan, Tanzania, Thailand, Timor-Leste, Tonga, Turkey, Türkiye, Uganda, United Arab Emirates, Uruguay, UAE, USA, Vanuatu, Vietnam, West Africa, West Indies, Zambia, Zimbabwe,

Cultivation

Trees are often grown from seeds but these do not breed true. Seeds grow most easily between 27°C and 32°C. It is better to use budded plants. Plants can also be grafted. Green fruit can be treated with ethylene to give an orange colour, if people think an "orange" fruit is not supposed to have green colour!

Propagation

Sow seed in a greenhouse as soon as it is ripe, after rinsing thoroughly. Stored seed should be sown in March in a greenhouse. Germination typically occurs within 2–3 weeks at 13°C. Seedlings are prone to damping off and must be watered carefully and kept well ventilated. The seed is usually polyembryonic — two or more seedlings arise from each seed, genetically identical to the parent and generally free of any virus present in the parent plant. Once large enough to handle, prick seedlings out into individual pots and grow on in the greenhouse for at least three growing seasons before attempting to move them outdoors. Plant out during summer and provide some frost protection during the first few winters outside. Propagation is also possible from cuttings of half-ripe wood taken in July or August in a frame, or by layering in October.

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 in perfumery and medicines. The flowers are rich in nectar and pollen, making them highly attractive to bees and other pollinators. Fruits provide food for birds and mammals, and the dense foliage offers shelter for nesting and roosting birds. Leaf litter beneath the trees creates overwintering sites for invertebrates, and the rough bark of mature trees can shelter beneficial insects. The strong citrus scent of the leaves and fruit can also act as a natural pest deterrent, confusing or repelling certain insects.

Production

Grafted trees produce in 2-3 years. Seedling trees take 3-5 years to fruit. Fruit take 6-8 months to mature after fruit set. A good tree can produce 100 fruit in a year. Fruit can be left on trees for several weeks after ripening for storage.

Other Information

Trees are seen scattered in many lowland areas in Papua New Guinea. Few good quality fruit are produced in wet tropical countries. It is a cultivated food plant.

Notes

There are 20 Citrus species. Several hybrids have been formed.

Nutrition

Synonyms

Also Known As

Afontongnu, Akutongnu, Arancio, Battavinarinja, Blood orange, Buddasini, Cam, Chini, Choreng, Chula, Demumuda danira, Dodan, Emicungwa, Guang gan, Hkun-pa, Jeruk manis, Kahel, Kamala nembu, Kittle, Lala, Lawidwi, Leainmaw, Lemun zaki, Limau manis, Majungwa, Makhun, Mchungwa, Mitha nimbu, Moli'aina, Moli dawa, Moli taiti, Monamona, Mor Rotuma, Muchungwa, Musambi, Narangam, Narangi, Naranja dulce, Naranji, Navel orange, Orenji, Orombo didu, Orombo igun, Peni dodan, Portakal, Satghudi, Sathagudi, Sathgudi, Sha-lawi, Sinaasappel, Sini, Somkliang, Somtra, Sweet orange, Te aoranti, Te oranti, Thodam, Tian cheng, Tungchin-thi, Tun-mapa, Valencia orange

References (95)

• Abbiw, D.K., 1990, Useful Plants of Ghana. West African uses of wild and cultivated plants. Intermediate Technology Publications and the Royal Botanic Gardens, Kew. p 42
• Ambasta, S.P. (Ed.), 2000, The Useful Plants of India. CSIR India. p 129
• Anderson, E. F., 1993, Plants and people of the Golden Triangle. Dioscorides Press. p 206
• Balkrishna, A., et al, 2022, Indigenous Uses of Plants among Forest-dependent Communities of Seijosa, Arunachal Pradesh. International Journal of Economic Plants 2022, 9(1):064-080
• Barwick, M., 2004, Tropical and Subtropical Trees. A Worldwide Encyclopedic Guide. Thames and Hudson p 116

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