Citrus
Family: Rutaceae

The orange is thought to be one of the oldest cultivated fruits, having been known for the last 3000 years. Probably originating from trop­ical Asia, it was cultivated in China before reaching Europe. The first orange to reach Europe was Citrus aurautium, introduced by the Crusaders and still widely cultivated, especially in Spain. Columbus brought the orange to the New World and, by the 17th century, trees were established in Florida. The orange now grows in warmer areas of all continents and is a very important item in international markets. Grown chiefly for its fruit and juice which are valuable sources of Vitamin C, it is eaten fresh, as well as being made into mar­malades and preserves, and used in cakes, salads, and meat and vegetable dishes. Some types are used in the manufacture of perfume. The deliciously scented blossom is widely used at weddings.

Species

Citrus aurantium, sour or Seville orange, is cultivated or naturalized in many parts of the world. It originally came from Southeast Asia, being introduced to Europe by the Spanish. Seville oranges have a flattened shape and are most widely used in marmalades and preserves. This species is grown as a street tree in several areas of southern Spain and is also being more widely used as an ornamental in parts of the United States, such as Florida, California and Arizona.

C. sinensis, sweet orange, is an evergreen tree which grows to about 8-12 m (26-40 ft( and bears round, orangecoloured, edible fruit. Its sweet, juicy pulp is contained in a smooth outer skin or rind. The pulp and juice are eaten and the essential oil of orange is extracted from the rind. Of the many varieties and cultivars available today, the 'Washington' navel is probably still the favourite eating orange, followed by 'Valencia'. There are many other cultivars but it is best to buy those that are offered locally. Blood oranges are very popular in Mediterranean countries and again there are several cultivars.

Cultivation

In climatic zones below zone 9, grow in a cool to intermediate greenhouse or conservatory in pots or tubs of soil-based pot­ting compost, with shade from direct strong sun. The plants can be stood outdoors for the summer.

In areas where oranges can be grown in the garden, plant the trees in ordinary garden soil, with effective drainage, in a full sun position. In very windy or frosty districts, some protection is necessary. Give regular, deep watering during flowering and fruit setting to ensure good quality fruit. Citrus trees have many surface roots, so avoid growing compet­ing plants such as grass under them. Mulch well to aid moisture retention, but keep mulch well clear of the trunk. Feed in late winter, and again in early and late summer.

Flowering takes place in spring and summer and is followed by the fruits, which can take many months to mature and ripen. Flowers and fruit may be present on the tree at the same time. Little pruning is needed once established. Citrus bark is very susceptible to sunburn, so trees should not be pruned in summer.

As the fruit is produced on the previous year's wood, any damage to the wood by frost, disease or negligence can cause the loss of the crop in the following year. Hand clip the fruit, leaving a bit of stem on it and taking care not to bruise the rind as this spoils the appearance and can set up conditions for moulds and rots to develop.

Climate

Zone 9 or 10. Best in warm, frost-free, low humidity climates.