Citrus fruits trees are small size and evergreen trees that are grown in tropical and subtropical climates. As this perennial crop does not tolerate cold climates, citrus fruits are normally harvested in the area situated at a latitude between 40º North and 40º South. They are therefore typically grown in "Mediterranean" type climates.

Generally, citrus trees start bearing fruits 3 - 5 years from planting (although economic yields start from the fifth year and the trees may take 8 to 10 years to achieve full productivity) and can be harvested 5 - 6 months from flowering depending on the variety and the environment. Only a small percentage of flowers produce fruits. Citrus trees require a rich, well-drained soil. Citrus growing needs periodical fertilization and irrigation of the soil, as well as pruning of the tree.

Unlike some other fruits, citrus fruits do not ripen further once they have been removed from the tree, so it is important that they are picked at the right stage of maturity. Maturity is measured depending on different characteristics such as color, juice content, level of soluble solid (sugar) and solids to acid ratio. Normally, citrus fruits are harvested by hand. Fruit is best harvested after 8:00 in the morning, when dew has dried up, since otherwise, if the fruit was still wet, it would become dark and get spoiled.

In addition, as citrus fruits are cold-sensitive (the plant dies at 3-5º C below 0ºC), growers must have special care to protect the trees against cold. Lemons and limes are the citrus fruits the most sensitive to cold weather. Strategies to protect from cold may include the selection of the proper citrus tree variety and rootstock for the location, selection of the proper planting site and allowing the tree to acclimate to the cold. Protection from frost methods include also the use of wind machines and the application of water.

The general way to pick the fruit is by pulling it from the stem, using gloves in order to avoid damaging the fruit. Once harvested, the fruit has to be graded, sorted, washed and waxed, before being packed for delivery to the fresh market. Fruit that does not meet the quality requirements for the fresh market is sent to the juice plants, while citrus fruits that were originally planted for juice production would follow a different processing chain.

See Uses section.

Availability of citrus fruits is variable according to the season and the producing area:

• Northern Hemisphere (winter citrus fruits): the season extends approximately from October/November to May/June.
• Southern Hemisphere (summer citrus fruits): the season extends approximately form April/May to November/December.
  

The citrus plant is very complex. There are many varieties of fruits in the different types of citrus fruits. Criteria for classification of the varieties also differ. For instance, in the case of oranges they can be divided according to the time of ripening (early, middle and late ripening varieties), the color (blond or blood) or the taste (sweet and sour).

Citrus fruits suffer from different diseases and pests that may considerably affect the fruit crop by destroying the trees and/or the fruits. The major disease problems include Citrus Canker, Citrus Variegated Chorosis (CVC) and Tristeza Virus. In consequence, citrus growers have to take special care in their growing and handling the fruit, in order to prevent the occurrence of these diseases and to fight against them. Citrus trees and fruits are also attacked by different insects. At present, many citrus growers use integrated production systems to face these problems (See, for instance: Integrated crop management systems in the EU and La producción integrada en cítricos, Infoagro).

Research and development activities are very useful in order to find the ways to prevent and fight more effectively against the incidence of these pests and diseases. See Research and Development in the section on Technology.