Dear dxb: The acorn crop size would be determined early in the year, it seems to me. I was told by a landscaper that severeing roots close to drip line in evergreens will made them produce cones. I remember an apple tree that doubled its yield just before it fell over from internal rot. I can't think of anything that would influence size of acorn crop except favorable conditions in spring, but I have no idea what the favorable conditions might be.