<Emphasis Type="BoldItalic">Key message</Emphasis> <p><b>Foliar calcium applied to sweet cherry spur leaves remains mobile to fruit until late season, partially compensating the reduction in xylem functionality and supporting calcium nutrition during rapid fruit growth.</b></p> Abstract <p>Calcium (Ca) is essential for cell wall and membrane integrity, affecting fruit firmness and postharvest quality in sweet cherry (<i>Prunus avium</i> L.). It is generally accepted that Ca accumulation in fruit declines during development due to reduced xylem functionality and phloem mobility. However, this study sought to assess whether Ca absorbed by fruiting spur leaves (FSL) could be translocated to fruit on the same spur until late in the season. The experiment was conducted on ‘Lapins’/‘Colt’ trees. Individual FSL were labeled with 0.05% ⁴⁴CaCl₂ at Stage I (24 days after full bloom, DAFB), Stage II (49 DAFB), and Stage III (70 DAFB). Leaves and fruit were sampled 48&#xa0;h after labeling and at harvest (87 DAFB) for isotopic analysis (ICP–MS) and Ca quantification (ICP–AES). Leaf enrichment differed significantly across developmental stages, with the highest absorption at SI (3319 δ ⁴⁴Ca‰). Fruit showed positive ⁴⁴Ca enrichment close to harvest, confirming short–distance translocation from FSL. Maximum fruit enrichment was observed at SII (140 δ ⁴⁴Ca‰). At harvest, ⁴⁴Ca values in fruit were ~ 66% lower than those measured 48&#xa0;h after enrichment (dilution by growth). These results confirm that foliar–applied Ca can be translocated to fruit by FSL until SIII (rapid fruit growth).</p> Graphical Abstract <p></p>