Bonide Products 56428 Bailey Nurseries and Bolide have teamed up to bring you an all natural way to acidify the soil to turn Hydrangeas blue 2.75 lb., Specialty Fertilizer, that turns hydrangeas blue when applied Sweetens acidic soil to pH which initiates color change for hydrangeas Apply to soil at plant root zone, and water in Enhances already blue flowers for vivid color, and vigor Affects soil pH alkalinity