scale, scars, skin breakdown, and thorn scratches Damage caused by dirt or other foreign material, disease, dryness, or mushy condition, hail, insects, riciness or woodiness, and sunburn. The USDA uses a separate grading system for oranges used for juice because appearance and texture are irrelevant in this case. There are only two grades: US Grade AA Juice and US Grade A Juice, which are given to the oranges before processing. Juice grades are determined by three factors: The juiciness of the orange The amount of solids in the juice (at least 10% solids are required for the AA grade) The proportion of anhydric citric acid in fruit solids Cultivation Climate Like most citrus plants, oranges do well under moderate temperatures—between —and require considerable amounts of sunshine and water. It has been suggested the use of water resources by the citrus industry in the Middle East is a contributing factor to the desiccation of the region. Another significant element in the full development of the fruit is the temperature variation between summer and winter and, between day and night. In cooler climates, oranges can be grown indoors. As oranges are sensitive to frost, there are different methods to prevent frost damage to crops and trees when subfreezing temperatures are expected. A common process is to spray the trees with water so as to cover them with a thin layer of ice that will stay just at the freezing point, insulating them even if air temperatures drop far lower. This is because water continues to lose heat as long as the environment is colder than it is, and so the water turning to ice in the environment cannot damage the trees. This practice, however, offers protection only for a very short time. Another procedure is burning fuel oil in smudge pots put between the trees. These devices burn with a great deal of particulate emission, so condensation of water vapour on the particulate soot prevents condensation on plants and raises the air temperature very slightly. Smudge pots were developed for the first time after a disastrous freeze in Southern California in January 1913 destroyed a whole crop. Propagation It is possible to grow orange trees directly from seeds, but they may be infertile or produce fruit that may be different from its parent. For the seed of a commercial orange to grow, it must be kept moist at all times. One approach