Spring phenology of fruit trees is advancing in many temperate regions. Recent frost damage events have led to yield losses and economic setbacks, for example during the severe frost incident in 2017 that affected apple orchards in Central Europe and the Alpine Region. This raises the question: does earlier phenology increase the likelihood of frost damage events? To address this, both the timing of frost events and the probability of frost occurrence need to be considered together.
In a new study we analyzed three spring phenological stages (budbreak, first bloom, and full bloom) for three commercially relevant apple cultivars (‘Golden Delicious’, ‘Nicoter’, ‘Topaz’). The study was conducted by Lars Caspersen, Katja Schiffers, Anton Milyaev and Eike Luedeling from the HortiBonn team, in coorperation with Daniel Neuwald from Kompetenz Zentrum Obstbau Bodensee (KOB). The dataset was collected at an orchard near Lake Constance by colleagues from the Kompetenzzentrum Obstbau Bodensee (KOB). We modified the PhenoFlex model to capture the sequence from budbreak through first bloom to full bloom within the same model, enabling us to delineate the frost-sensitive period and estimate frost risk more precisely. The analysis was conducted under both current and projected future conditions across several climate scenarios.
The results indicate that two opposing trends interact. On the one hand, earlier spring phenology increases exposure to frost. On the other hand, warmer winters reduce the overall likelihood of frost events. For most scenarios these effects offset each other. While the share of frost-free seasons is projected to increase, the possibility of more severe frost events remains relevant for growers.
For further details, please see our recent publication:
Caspersen, L., Schiffers, K., Milyaev, A., Neuwald, D., Luedeling, E., 2025. Spring phenology projections for apples in southwestern Germany indicate persistent frost risk levels. Agricultural and Forest Meteorology 374, 110824. doi: https://doi.org/10.1016/j.agrformet.2025.110824
