köldtimmar

Köldtimmar, a Swedish term, translates to "chill hours" or "cold hours" and refers to the accumulated number of hours that a plant is exposed to temperatures within a specific low range, typically between 0 and 7 degrees Celsius (32 and 45 degrees Fahrenheit). This period is crucial for the proper development and dormancy of many temperate-zone plants, particularly fruit trees and certain perennial flowers.

During winter, many plants require a sufficient period of cold temperatures to break their dormancy. This cold exposure is essential for triggering the physiological processes that lead to flowering and fruit production in the following growing season. Without adequate köldtimmar, plants may fail to bloom properly, produce fewer fruits, or exhibit stunted growth.

The specific number of köldtimmar required varies significantly among different plant species and even cultivars. For example, apple varieties often need between 600 to 1,000 köldtimmar, while some peach varieties may require more. Horticulturalists and fruit growers often consider the local climate's average köldtimmar when selecting varieties suitable for their region. Monitoring and understanding these cold requirements are vital for successful perennial crop cultivation in climates that experience distinct winter seasons.