Growing medium for container gardening

In order to grow healthy plants, a growing medium must be able to consistently supply water and nutrients, as well as, provide a structure in which your plants can take root. There are two categories of growing mediums typically used in container gardening: soil mixtures and soil-less mixtures.

Soil mixtures, which are widely referred to as potting mixes, are often heavy and hold water and nutrients more easily than soil-less mixtures. They are traditionally composed from soil, compost or peat moss, and vermiculite or perlite. Composted manure can also be added to soil mixtures to increase water-holding capacity and the abundance of nutrients.

These mixtures are typically cheaper than soil-less mixtures, and those that contain compost or composted manure require fewer applications of fertilizers and micro-nutrients because they already contain the majority of nutrients that your plants will need to grow.

However, I generally discourage the use of soil mixtures in container gardening because they are prone to compacting, which can inhibit root growth, affect aeration, and cause poor drainage. They are much heavier than soil-less mixtures making moving and handling container gardens more difficult. Soil mixtures are also more likely to contain weeds, seeds and disease, particularly when they contain compost or unpasteurized soil. The flaws seem to outweigh the benefits in most cases so soil-less mixtures are a better option for container gardening.

As the name suggests, soil-less potting mixtures do not contain soil. Instead, they are commonly made from sphagnum moss, peat moss, coconut coir fiber, perlite or vermiculite. This type of growing medium is sterile, offering the added benefit of being weed, seed, bacteria and disease free. For most gardeners, this offers the assurance that your seedlings will not be susceptible to attack by pre-existing diseases and organisms, allowing your plants to thrive.

Potting soil-less mixtures are lighter than traditional soil mixtures, which make them a good choice for raised container gardens and vertical gardens, which have the potential to buckle under heavy loads. Lighter medium also means less compaction, greater aeration, and more consistent drainage. Because soil-less mixtures can be created from a variety of components, they allow you to customize the physical structure of the soil to meet specific plant needs.

In comparison to soil mixtures, soil-less mixtures do require more frequent applications of organic fertilizers and micro-nutrients, as they often lack the full range of nutrients necessary for healthy plant growth. However, this factor can actually be an advantage because by ensuring that your plants’ specific nutrient needs are being met, you are also ensuring that your plant will yield abundant produce of the highest quality. Keep in mind that careful attention must be paid to the level of salts present in fertilizers to prevent buildup in container gardens. It should also be noted that due to the ease with which soil-less mixtures drain, fertilizers and micro-nutrients may need to be applied regularly.