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Ingredients in Miracle-Gro Potting Soil

By J. Lang Wood ; Updated July 21, 2017

Many products are available to help indoor gardeners get maximum results from their efforts, including fertilizers, root hormone products, pesticides and growing media. Miracle-Gro products, made by the Scotts Company, is a well-known brand with a broad line of potting soil products for a variety of special uses. Miracle-Gro Potting Soil is specially formulated to provide all the ingredients that plants require for healthy indoor growth.

Sphagnum Moss

According to Brandeis University, sphagnum moss grows as a strong, boggy mat that floats on top of water with shallow roots and a strong ability to hold water. It is generally light green, but also grows in colors of yellow, pink, brown or deep red. Sphagnum moss has a delicate system of capillary tubes that allow the plant to absorb water like a sponge. Its main use in gardening is to keep soil moist, particularly indoors where temperatures can dry soil quickly. It also contains a chemical called sfagnol, which possesses antiseptic qualities, preventing the growth of bacteria.


Perlite is a generic name for a type of naturally occurring volcanic glass. When heated, this glass expands to 4 to 20 times its natural volume. In horticultural use, perlite provides soil aeration and moisture retention for indoor gardening, and is also used in soilless hydroponic gardening. Perlite advantages are that it is sterile and weed-free, and provides a neutral pH for plants.


Compost is made of organic matter, like leaves, twigs, grass clippings and kitchen waste, that decomposes into a rich, loamy, soil-like material. It is essentially an accelerated process that nature uses to return nutrients to soil. It provides a slow-release source of nutrients for plants, adds beneficial organisms to soil and increases moisture-holding ability in soil. Plants grow well in compost because nutrients are available over time. Using compost also helps to reduce pest problems.

Calcium Phosphate

Calcium phosphate is added to potting soil to provide the calcium that is important for chromosomal development and cell division in plants. It also provides resistance to plant diseases.

Ammonium Nitrate

Ammonium nitrate provides nitrogen to plants, an essential component that promotes growth and production of amino acids. You must use nitrogen with discretion because it causes such fast growth that new, thin plant walls may be vulnerable to diseases.

Potassium Sulfate

Potassium is a regulator of cell activity and thickens the outer walls of plant cells, which allows stronger growth and better resistance to disease. It does not become part of the cell structure, but is a mobile component that helps to regulate other nutrients.

Ammonium Phosphate

Phosphorus is essential to cell division and utilization of carbohydrates for plant nutrition. It is an important component in root growth and seed development. An excess of phosphorus can increase susceptibility to viruses and other disease agents.