Citrus sinensis - (L.)Osbeck.
Sweet Orange
Author (L.)Osbeck. Botanical references 200
Family Rutaceae Genus Citrus
Synonyms Citrus aurantium sinensis - L.

Known Hazards None known
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[200].
Edibility Rating 4 (1-5) Medicinal Rating 3 (1-5)

Physical Characteristics
An evergreen Tree growing to 9m.
It is hardy to zone 9 and is frost tender. It is in leaf all year. The flowers are hermaphrodite (has both male and female organs) and are pollinated by Apomictic (reproduce by seeds formed without sexual fusion), insects. The plant is self-fertile.

The plant prefers medium (loamy) and heavy (clay) soils and requires well-drained soil. The plant prefers acid, neutral and basic (alkaline) soils and can grow in very acid and very alkaline soils. It cannot grow in the shade. It requires moist soil.

Habitats
Woodland Garden; Sunny Edge; South Wall By; West Wall By;

Edible Uses
Edible Parts: Flowers; Fruit.

Edible Uses: Condiment; Tea.

Fruit - raw. Sweet and delicious[1, 3, 46, 61]. The juice is often extracted from the fruit and sold as a refreshing and healthy drink or used in jellies, ice cream etc[183]. The rind of the fruit is often used as a flavouring in cakes etc or made into marmalade[1, 46, 183]. Flowers - cooked as a vegetable or made into a tea[183].

Medicinal Uses
Appetizer; Blood purifier; Carminative; Miscellany; Skin; Tonic.

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[238]. Some of the plants more recent applications are as sources of anti-oxidants and chemical exfoliants in specialized cosmetics[238]. The fruit is appetizer and blood purifier[240]. It is used to allay thirst in people with fevers and also treats catarrh[240]. The fruit juice is useful in the treatment of bilious affections and bilious diarrhoea[240]. The fruit rind is carminative and tonic[240]. The fresh rind is rubbed on the face as a cure for acne[240]. The dried peel is used in the treatment of anorexia, colds, coughs etc[218].

Other Uses
Essential; Oil.

A semi-drying oil obtained from the seed is used in soap making[46, 61]. An essential oil from the peel is used as a food flavouring and also in perfumery and medicines[1, 46, 61].

Scented Plants
Flowers: Fresh
The flowers are sweetly scented.
Leaves:

Cultivation details
Prefers a moderately heavy loam with a generous amount of compost and sand added and a very sunny position[1, 200]. Prefers a pH between 5 and 6[200]. Tolerates a pH in the range 4.3 to 8.3. Plants are intolerant of water logging[3]. When growing plants in pots, a compost comprising equal quantities of loam and leafmould plus a little charcoal should produce good results[260]. Do not use manure since Citrus species dislike it[260]. 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[260]. The sweet orange is widely grown for its edible fruit in warm temperate and tropical zones, there are many named varieties[183]. In Britain it can be grown in a pot placed outdoors in the summer and brought into a greenhouse during the winter[3]. Plants are almost hardy in the mildest areas of Britain[1] but the fruit is insipid if it is developed when the mean temperature is below 18°c[3]. 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[K]. The flowers are sweetly scented[245]. 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[238].

Propagation
The seed is best sown in a greenhouse as soon as it ripe after thoroughly rinsing it[164, 200]. Sow stored seed in March in a greenhouse[3]. 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[200]. 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, July/August in a frame.

References
[K] Ken Fern, Notes from observations, tasting etc at Plants For A Future and on field trips.

[1] F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956 Oxford University Press 1951 Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaces in 1992 by a new dictionary (see [200]).

[3] Simmons. A. E. Growing Unusual Fruit. David and Charles 1972 ISBN 0-7153-5531-7. A very readable book with information on about 100 species that can be grown in Britain (some in greenhouses) and details on how to grow and use them.

[46] Uphof. J. C. Th. Dictionary of Economic Plants. Weinheim 1959. An excellent and very comprehensive guide but it only gives very short descriptions of the uses without any details of how to utilize the plants. Not for the casual reader.

[61] Usher. G. A Dictionary of Plants Used by Man. Constable 1974 ISBN 0094579202. Forget the sexist title, this is one of the best books on the subject. Lists a very extensive range of useful plants from around the world with very brief details of the uses. Not for the casual reader.

[164] Bird. R. (Editor) Growing from Seed. Volume 4. Thompson and Morgan. 1990. Very readable magazine with lots of information on propagation. A good article on Yuccas, one on Sagebrush (Artemesia spp) and another on Chaerophyllum bulbosum.

[183] Facciola. S. Cornucopia - A Source Book of Edible Plants. Kampong Publications 1990 ISBN 0-9628087-0-9. Excellent. Contains a very wide range of conventional and unconventional food plants (including tropical) and where they can be obtained (mainly N. American nurseries but also research institutes and a lot of other nurseries from around the world.

[200] Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press 1992 ISBN 0-333-47494-5. Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.

[218] Duke. J. A. and Ayensu. E. S. Medicinal Plants of China Reference Publications, Inc. 1985 ISBN 0-917256-20-4. Details of over 1,200 medicinal plants of China and brief details of their uses. Often includes an analysis, or at least a list of constituents. Heavy going if you are not into the subject.

[238] Bown. D. Encyclopaedia of Herbs and their Uses. Dorling Kindersley, London. 1995 ISBN 0-7513-020-31. A very well presented and informative book on herbs from around the globe. Plenty in it for both the casual reader and the serious student. Just one main quibble is the silly way of having two separate entries for each plant.

[240] Chopra. R. N., Nayar. S. L. and Chopra. I. C. Glossary of Indian Medicinal Plants (Including the Supplement). Council of Scientific and Industrial Research, New Delhi. 1986
Very terse details of medicinal uses of plants with a wide range of references and details of research into the plants chemistry. Not for the casual reader.

[245] Genders. R. Scented Flora of the World. Robert Hale. London. 1994 ISBN 0-7090-5440-8
An excellent, comprehensive book on scented plants giving a few other plant uses and brief cultivation details. There are no illustrations.

[260] Phillips. R. & Rix. M. Conservatory and Indoor Plants Volumes 1 & 2 Pan Books, London. 1998 ISBN 0-330-37376-5. Excellent photos of over 1,100 species and cultivars with habits and cultivation details plus a few plant uses. Many species are too tender for outdoors in Britain though there are many that can be grown outside.