Espoma Organic Iron & Soil Acidifier, 6 lbs. is specially formulated for organic gardening to help turn hydrangeas blue by lowering soil pH. This all-natural, pelletized mix supports acid-loving plants like blueberries and hydrangeas to achieve optimum growth. Safer than aluminum sulfate, it provides a gentle yet effective way to acidify your soil. For results, apply in the spring and repeat every 60 days until the desired pH level is reached. The product comes in a convenient 6 lb. ready-to-use bag, covering up to 50 square feet. Model Number: