Aluminum Sulphate helps create an acid soil condition for plants such as azaleas, gardenias, camellias, rhododendrons, hydrangeas and others. Aluminum Sulphate is known to intensify blue color in hydrangeas. Even better blues can be achieved by a yearly application of aluminum sulfate, but follow application rates carefully! Aluminum Sulphate can help supply a correct fertilizer program for your plants. It will not only assure more robust and healthy plants, but aid in color intensity. Alternatively to applying aluminum sulfate, you can apply a nitrate-based fertilizer with an NPK ratio of 5-1-6. Avoid using bone meal or superphosphate when planting your hydrangeas. For best pinks in your hydrangeas, use a nitrate-based fertilizer with a NPK ratio of 5-2-2.