Miracle Gro contains urea phosphate, potassium chloride, sodium molybdate, ammonium phosphate, zinc sulfate, copper sulfate, chlorine, boric acid, manganese EDTA, disodium salt and ferric sodium EDTA. Some of these ingredients provide macronutrients, which plants need plenty of to grow; others provide micronutrients, which plants need less of but are still vital to the plant's health.
Garden Guides notes that urea phosphate is comprised of 17 percent nitrogen and about 44 percent phosphorus oxide. Phosphorus is responsible for nearly all of the developmental aspects of plant growth. Urea phosphate is created by mixing urea with orthophosphoric acid, and it is the primary contributor of nitrogen to plants.
Ammonium phosphate contains micronutrients, such as calcium oxide, magnesium oxide and sulfur. In solid form, ammonium phosphate is 11 percent nitrogen and 48 to 55 percent phosphorus oxide. Zinc sulfate is responsible for regulating carbohydrates and protein in plants. Copper is responsible for metabolizing nitrogen. Chlorine helps plants absorb minerals and helps with photosynthesis.
Plants need boric acid for developing cells and cell walls, and it is necessary for calcium absorption. Ethylenediaminetetraacetic acid, otherwise known as EDTA, acts as a chelating agent, which binds macronutrients, so plants can absorb them. Manganese EDTA is responsible for nitrogen metabolism, photosynthesis and respiratory function in plants. Ferric sodium EDTA injects iron into plants, which is crucial for synthesizing chlorophyll and promoting functioning enzymes. Sodium carries water to plant cells, and molybdate prevents nitrogen deficiencies.