Early is where it's at:  Individual Honeycrisp fruits analyzed for mineral content around the end of the cell division period of fruit development (+40 mm) have been found to be highly variable in mineral content, particularly calcium.  Four years of research results in the Hudson Valley show that early season fruit calcium content can vary as much as 4.2X from a low Ca fruit to a high Ca fruit (figure 1).  These finding suggest that our calcium troubles start early in the growing season and therefore should be addressed early as well.  The calcium cation is not very mobile with plant tissue and doesn't move from cells with a surplus to cells in deficit.  Calcium cations need to be available for cell walls and membranes locally, and when needed.  Too far away and/or too late is of little help. Since calcium plays a role within the plant in hormonal signaling, the cations cannot remain "free" within cell cytoplasm or within the spaces between cells and cell walls.  Free calcium cations that are not incorporated promptly into cell membranes, cell walls, and endoplasmic reticulum are quickly deactivated and made unavailable through sequestration within cell vacuoles.