Hy-Pro Cal-Mag provides a precise balance and optimal ratios of calcium, magnesium and iron, which are critical in all phases of growth, especially in heavy fruiting plants and fast-flowering annuals. The high level of calcium and magnesium in our formula improves cell wall strength and chlorophyll production. Hy-Pro Cal-MAG is vital for soft water areas where tap water contains little or no calcium or magnesium. Hy-Pro Cal-Mag is also fortified with a proprietary blend of selected trace elements to help maximize yield in fruiting and flowering plant varieties. Iron, for example, acts as a catalyst for essential reactions within the plant, especially related to metabolism. It has to be the right form of chelated iron. And it has to be in the right proportions, relative to the other nutrients in your supply.