Fertilome's Soil Acidifier Plus Iron contains all the essentials for acidic soil loving plants such as Roses, Gardenias, Azaleas, Holly, Rhododendron, Magnolias, and various fruit and vegetable bearing plants. The active ingredients in this product are Iron Sulfate, Copper Sulfate, Magnesium Sulfate and Zinc Sulfate. Each of these are water soluble "metal salts" that help your plants get both sulfur and each of the associated metals. Just like you, plants need small amounts of these metals for proper functioning of their cells and without them they can't grow big and strong!