Ask any seasoned gardener and they’ll tell you that the secret to growing an abundant garden is good soil. And what goes for beds and borders goes for containers too.
Good Garden Soil Does Not Equal Good Container Soil
Well-prepared garden soil is great for growing things in the ground, but even the best garden loam usually makes a rather poor growing medium when used alone in a container. The big difference is texture. In a closed environment like a container drainage and air circulation are key so the soil needs to be blended with these characteristics in mind.
What Is a Commercial Potting Mix?
Commercial potting mixes are designed to ensure drainage and aeration. They are available as soil-based blends and soilless mixes. Soil-based blends are usually made of humus, compost or loam mixed with an amendment such as vermiculite, peat moss, perlite and coir fiber. Soilless mixes are usually a combination of peat with vermiculite, bark, coir or perlite.
The soil-based blends are heavier, which may be a plus in windy areas, and will hold water and nutrients longer. They can be slow to drain so keep an eye out for soggy soil.
Soilless mixes are disease- and weed seed-free and as long as your plants are healthy during the growing season, you can reuse it. Refresh it by adding some new mix to fluff it up. Eventually the mix will lose its texture and need to be replaced.
These mixes are light and airy which prevents soggy soil, but you will need to water more often during the heat of summer. The additional water will deplete nutrients so some plants such as annuals will require more frequent feeding.
To make light soilless mixes easier to work with add a little water before planting.
Designer Blends
Potting soils are available in combinations designed for a specific type of plant. For instance, sharp drainage for succulents, moisture retention for houseplants, or high acidity for blueberries.
Many commercial potting mixes also include fertilizers and water-retentive polymers.
Soilless Container Mix Recipe
- 3 parts peat
- 1 part coarse sand
- 1 part perlite/vermiculite
- 6 ounces of lime per bushel of mix to reduce acidity
Soil-Based Container Mix Recipe
- 1 part compost
- 1 part peat
- 1 part perlite/vermiculite
- 1 part well-composted manure