Climate is an important limiting factor to the growth and development of apple trees, especially temperature. In my project I focus on the impact of temperature on apple trees. For example, temperature thresholds for differnt phonological processes in apples, and temperature; how temperature affects on growth rates for different plant components such as root, shoot/trunk, seedling, buds, flower and fruits; and winter injury, frost effect and cold resistance. Finally, I estimated the change of Danish temperature form 1955 to 2004.