Subtropical Fruit Crop

any of a group of perennial evergreen or, less frequently, deciduous trees and shrubs cultivated in the subtropics. These crops include oranges, tangerines, lemons, grapefruits, and other citrus fruits, olives, avocados, figs, pomegranates, persimmons, feijoa, medlars, dates, almonds, pecans, pistachios, and carob, many of which are grown in the USSR.

Subtropical fruit crops are characterized by relatively poor winter hardiness. They have a long growing period and require stable conditions during their winter dormant period. Individual crops vary greatly in their frost resistance. The lemon tree is the least winter hardy; during its winter dormant period it can tolerate short frosts of one or two hours at 5°–6°C, but it is easily injured at temperatures of –7°C or –8°C. The most frost resistant are the deciduous trees, including fig, pomegranate, and persimmon, which can tolerate temperatures as low as – 17°C relatively easily if conditions are controlled properly. Subtropical crops require various amounts of heat during their growing periods. A total annual temperature of not less than 4000°–4500° is required for the normal growth and maturation of such fruits as tangerines and oranges.