pistachios can tolerate temperatures down to -20°C, and in Turkey pistachios can withstand win-
ter temperatures of down to -30°C without any injury. P. vera aged by late spring frost. However, plantations established in frost pockets may be at risk. Flow- ers may also be damaged by burn caused by dry and hot winds during the spring. Like other fruit trees pistachio requires chilling during the winter period. Under mild climatic conditions, inadequate chilling causes problems such as very low yield, unsuitable timing and low percentage of budbreak, late flowering, death of stigma, very late vegetative and generative development, late ripening, less leaf and pollen production and irregular sprouting of the buds (Kuden et al., 1995). Studies have shown that the cultivar ‘Kerman’ needs about 1000 hours chilling (Crane and Takeda, 1979) whereas the cultivar ‘Uzun’ needs 600 hours and ‘Ohadi’ needs more than 1000 hours (Kuden et al., 1995). Ku- den et ess chilling than females.
Summer temperatures are another very important climatic factor influencing pistachios. If the sum-
mer temperatures are insufficient then the kernel does not develop properly which prevents split-
ting and dehulling.