Aluminum Sulphate Hi-Yield can help establish an acidic soil environment that is beneficial for plants, as well as intensify the blue color in Hydrangeas. It can be used on Azaleas, Gardenias, Camellias, Rhododendrons, Blueberries, and other plants indicated on the product label. The suggested application rates include 1 lb. for every 3 ft. of height for shrubs, 1 lb. for every inch of tree diameter, and 5 lbs. for every 100 sq. ft. to correct alkaline soil.