The growing season in Europe has extended by an average of 10.8 days since the early 1960s, primarily due to changes in air temperature. This extension is evident in the phenological shifts of spring events, such as leaf unfolding, which have advanced by 6 days, and autumn events, such as leaf colouring, which have been delayed by 4.8 days. The International Phenological Gardens (IPG) network, covering a wide range of latitudes and longitudes in Europe, recorded these changes from 1959 to 1993. A unified phenological model applied to the IPG data showed that the onset of spring events is sensitive to climatic change, advancing by up to 6 days per 1 °C increase in winter air temperature. Regional studies in Hungary and Germany also support these findings. The lengthening of the growing season is expected to contribute to increased biomass formation and accelerated tree growth, reflecting a global increase in biospheric activity.The growing season in Europe has extended by an average of 10.8 days since the early 1960s, primarily due to changes in air temperature. This extension is evident in the phenological shifts of spring events, such as leaf unfolding, which have advanced by 6 days, and autumn events, such as leaf colouring, which have been delayed by 4.8 days. The International Phenological Gardens (IPG) network, covering a wide range of latitudes and longitudes in Europe, recorded these changes from 1959 to 1993. A unified phenological model applied to the IPG data showed that the onset of spring events is sensitive to climatic change, advancing by up to 6 days per 1 °C increase in winter air temperature. Regional studies in Hungary and Germany also support these findings. The lengthening of the growing season is expected to contribute to increased biomass formation and accelerated tree growth, reflecting a global increase in biospheric activity.