Miracle-Gro is a popular, easy-to-use fertilizer for ornamentals, vegetables, fruit trees, lawns and houseplants. It is made by the Scott's Company, with the goal of making it easy for all gardeners to grow large, healthy plants. Although it's a synthetic plant food, Miracle-Gro is considered a safe product, but it is not permitted for use in certified organic farms.
According to the Scott's Company, their standard Miracle-Gro product has an N-P-K ratio of 15-30-15, making it high in nitrogen, phosphorus and potassium, with the highest nutrient concentration being phosphorus, an essential plant nutrient.
One of the main ingredients of Miracle-Gro is the chemical ammonium phosphate, which can have toxic effects on soil and irritate human mucus membranes, according to Cameo Chemicals. This ingredient is one of the most commonly used fertilizers because it has a high percentage of phosphorus---up to 46 percent, according to Simplot.com.
According to MedTerms.com, urea is a substance that contains nitrogen which the kidneys clear from blood before the body excretes it as urine. Urea is a common additive in fertilizers; some people even believe that watering plants with their urine can be beneficial. Urea is found in natural forms in urine and was the first chemical compound to be synthesized. Urea is ammonium cyanate.
This chemical ingredient found in Miracle-Gro is a white crystal or crystalline powder that helps plants increase their growth and productivity. However, potassium chloride can be harmful to humans if it is swallowed; it may cause irritation of the skin, eyes and lungs if high concentrations of this substance are inhaled.
Although some chemical fertilizers contain heavy metals such as lead, arsenic, mercury, barium, cadmium, copper, nickel and others as fillers or inert ingredients, according to the book "Fateful Harvest," Miracle-Gro was tested along with other home fertilizers and was found to be "clean" of toxic metals.