Potting Soil Basics

Choosing the Right Potting Soil

When you visit the nurseries or garden centers you are often faced with long rows of palleted bags of soil. Each pile appears to be a different brand or type of soil, and prices vary widely. How do you know which to use? Even their descriptions can be bewildering; potting soil and potting mixes, planting soil and mixes, top soil, soil amendment, soil conditioner, mulch... This section will help you understand what's available and when you should choose a particular type over another.

Soil materials are available by the bag, by the yard or by the truckload. The smaller the quantity, the higher the price you will pay for the same amount. Buying a small bag of soil off the shelf will cost much more per quart as buying a two-cubic-foot bag and still cheaper if you purchase a yard or a truckload. Don't forget to factor in delivery charges.

Potting Soils and Mixes

 Potting soils, also called potting mixes, are a blend of organic and inert materials that are used to fill containers such as pots, barrels, tubs, boxes or raised beds. Potting mixes do not contain soil, but there really isn't any reason why you can't add a small amount of healthy soil to your mix. Correct aeration and drainage are the main criteria for any potting mix.

The major ingredients are generally made with materials available locally, and may include green waste, forest products, sawdust, seaweed, peat, bark, coir (coconut husk fiber) and animal manures. Minor ingredients may include fish waste, bat guano, worm castings, various organic fertilizers (alfalfa or cottonseed meal, phosphate dust, others) and sometimes mycorrhiza and beneficial soil bacteria. Inert ingredients may include perlite for water retention and sand for drainage. Ingredients may be added to neutralize the pH and these may include dolomite, lime or oyster shell.

Some potting soils are purposely made acidic. Why so? These are beneficial for plants that require an acidic soil around their roots, plants including blueberries, azaleas, rhododendrons, gardenias, conifers and most evergreens. The acidity enables these plants to absorb the nutrients they need to flourish and grow. This potting soil will state clearly on the bag that it contains an  ACID MIX. Planting most hydrangeas in an acidic soil will turn the flowers blue, while planting them in a limed soil will cause the flowers to become pink. How to remember that? Acid = Blue (A and B are next to each other).

Planting Mixes and Soils

Planting mix, also known as planting soil, is a blend of organic materials that will be worked into an existing flower bed or  custom made to  mixotting soil is available by the bag, the yard or the truckload. The smallest quantities are the most expensive.

Soil Conditioners and Amendments

Potting soil is available by the bag, the yard or the truckload. The smallest quantities are the most expensive.

Top Soils and Mulches

Potting soil is available by the bag, the yard or the truckload. The smallest quantities are the most expensive.