The term describes the cumulative number of hours during the dormant period (typically winter) when temperatures fall within a specific range, usually between 32F and 45F (0C and 7C). This period of sustained cold is essential for many deciduous fruit trees, including certain apple varieties, to properly break dormancy and initiate flowering and fruit set in the spring. Insufficient accumulation of these cold units can result in delayed or reduced flowering, irregular fruit development, and diminished yields.
Meeting this requirement is crucial for successful cultivation in specific geographical regions. The necessary accumulation ensures consistent and predictable fruit production. The origin of this understanding lies in agricultural science, where researchers identified a correlation between winter temperatures and the subsequent productivity of orchards. Matching a cultivar’s need to a location’s climate is vital for optimizing orchard performance and maximizing economic returns.
