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The Composition of Miracle Gro Fertilizer

Updated February 21, 2017

Miracle Gro is a brand name of plant food for lawns, houseplants, vegetables, ornamentals and other plants. It is a synthetic fertiliser, meaning it is not approved for certified organic farms, but its ingredients work well for most gardens.

N-P-K Ratio

Different Miracle Gro products have slightly different N-P-K ratios. The standard product contains a ratio of 15-30-15, which gives it sufficient nitrogen, phosphorus and potassium to nourish most types of plants and help flowering plants produce more blooms.

Ammonium Phosphate

Ammonium phosphate is a common ingredient in synthetic fertilisers. Its high concentration of phosphorus represents 46 per cent of its total volume, according to the website Simplot Plant Nutrients. Breathing the fumes of ammonium phosphate can irritate the mucus membranes.

Lesser Ingredients

Miracle Gro also contains urea, potassium chloride and inert ingredients. Urea is ammonium cyanate, a common plant food ingredient. Potassium chloride helps plants grow and produce flowers and fruit. It can harm the skin, the eyes and---if inhaled---the lungs.

Miracle Gro is free of the heavy metals often found in the inert materials of other fertilisers, according to the book "Fateful Harvest."

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About the Author

Barbara Fahs lives on Hawaii island, where she has created Hi'iaka's Healing Herb Garden. Fahs wrote "Super Simple Guide to Creating Hawaiian Gardens" and has been a professional writer since 1984. She contributes to "Big Island Weekly," "Ke Ola" magazine and various websites. She earned her Bachelor of Arts at University of California, Santa Barbara and her Master of Arts from San Jose State University.