Everything You Ever Wanted to Know about Potting Soil

Potting mix plays an important role in the health and vitality of potted plants, bearing the task of mitigating limited root space and an unnatural habitat. In order to understand what constitutes a great potting mix, one must first understand the functions that a potting mix performs.

A good potting mix will:

  1. Hold sufficient moisture and nutrients around the roots of your plants. Unlike natural soil, plants grown in containers have limited space to grow their roots. In the limited space, water and nutrients should be retained to support healthy plant growth.
  2. Provide oxygen flow. Since a lack of air can cause your roots to rot, a light and porous potting mix is vital to allow the root system to breathe.
  3. Provide support and anchorage for the plant. The mix needs to provide enough physical stability to allow the roots to grip the soil and the plant to stand upright.

A quality potting mix provides a good balance of these three requirements.

Choosing a Potting Mix

Though there are a number of different ingredients and approaches that can be utilized to achieve these goals, a properly made potting mix should feature a few common attributes that any consumer can identify.

  1. Water Retention Properties – A quality potting soil should list an ingredient with moisture retention capabilities, such as sphagnum peatmoss, coir, a wetting agent, that will retain moisture in the mix for your plant.
  2. Slow Release Plant Food – A slow release Fertilizer like Osmocote® Smart-Release® Plant Food will provide food for your plant, giving it the nutrients it needs to thrive in a pot.
  3. Proper Weight – Potting mix should be relatively light. A heavy weight usually indicates limited air space in the potting mix for plant roots.
  4. Quality Ingredients – Look for a potting mix with sphagnum peat moss, composted pine bark, and perlite. More information on these ingredients is given below.

Learn More About Specific Ingredients

A great potting mix should contain three ingredients: Sphagnum peat moss, composted pine bark, and perlite. Let’s review each of these components in more detail:

Sphagnum Peat Moss

Sphagnum peat moss comes from peat bogs in the northern U.S. and Canada. It is partially decomposed plant material through lack of oxygen. Good quality sphagnum peat moss can retain up to 60% of its volume in water and desirable amount of nutrients for plant roots. The light weight and fibrous material can provide good air space properties to the potting mix.

Composted Pine Bark

Composted pine bark is included in potting soil mixes in order to generate big pores for aeration and better drainage. It also provides stability for the plants’ root systems. Pine bark works well in combination with sphagnum peat moss, plant food, and perlite to produce a superior growing medium. Most pine bark is sourced from North American forests.


Perlite is an expanded volcanic rock which is white, lightweight aggregate. This is stable and sterile material. This is a good ingredient to provide aeration in potting mix for plant roots.

Specialty Potting Mixes

There are a few plants that require specialty potting mixes, due to their unique cultural demands. The two most common categories are Orchids and Cactus.


Most of the orchids are epiphytes, meaning that they do not grow in the ground but in tress or on rocks. Their roots require excessive air, therefore excellent drainage and a lot of airflow are keys for this type of orchids. All-purpose potting mix might be too wet and not provide sufficient air for the orchids.

Cactus and Succulents

These desert plants require a sandy, fast-draining soil. Often, mixing a poting mix 50/50 with sand is an effective way to create the proper environment for desert plants.

Other Types of Soil Mixes

Your local garden center will have numerous soil products from which you can choose. Keep in mind that if you are using containers, you’ll want potting mix, whereas the other products are for your garden or for landscaping.

Garden Soil or Gardening Mix

These are heavy and rich mixes with compost and composted bark fines and low volume of sphagnum peat moss. These products should be mixed into ground soil to improve soil quality by adding rich organic matters. Therefore, this is not engineered to use in container to grow plant directly.


A mulch is a layer of material covering the surface of ground. In general, shredded wood mulch products are available in market. Application of mulch material can save water by reducing evaporation from the ground, and help reduce the number of weeds naturally.

Manure Products

Manure products are great resources for soil improvement by adding organic matter content in mineral native soil. It contains generally high in soluble nutrients such as nitrogen. Therefore, only limited volume of manure products can be mixed into potting mixes.

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