Climate change is responsible for major alterations in the phenology of fruit trees in Germany. Observations over the past 70 years at 3 study sites in Germany have shown the flowering of apple trees and subsequently, fruit development to set is continuously earlier, with serious implications for fruit quality as well as storability. Calcium (Ca) plays an important role in stabilizing cell walls in all fruit including apple; sufficient calcium supply is, therefore, essential for good storability and for controlling postharvest disorders. However, as Ca is phloem immobile, the transport of the mineral into the fruit occurs solely with the transpiration stream through the xylem. Ca accumulates in the first weeks after flowering, in which the fruit shows the highest transpiration per unit (surface or mass) and subsequently the greatest transport of water. With an earlier flower onset, Ca uptake may suffer as the evapotranspiration and therefore the transport of Ca is reduced due to fewer sunlight hours in a shorter photoperiod and a smaller thermal amplitude early in the season. However, Ca deficiency and an unfavorable relation to its antagonist potassium can increase the risk of the accelerated loss of firmness or the emergence of disorders such as bitter pit or flesh browning. On account of this significant role of Ca for long-term fruit storability, a project was launched with the objective to assess the long-term effects of climate change on the Ca nutrition of apples cultivated in Germany. Climate data of the past 60 years will be analyzed and related to the recordings of apple tree phenology development stages in the respective years, in order to estimate the evapotranspiration potential during the main period of Ca uptake. Historic Ca data of ‘Golden Delicious’ apples, recorded starting in the 1970s at the Lake of Constance Research Center for Fruit Cultivation (KOB), will be analyzed to investigate trends in the Ca nutrition of apple fruit. Ultimately, the project aims to develop a multivariate model for the prediction of Ca content in apples at harvest, that incorporates factors such as the weather during the season, soil type, tree age, cultivar and cultivation practices. In the long term, this is intended to support fruit production in adaption to challenges presented by climate change.