Whether growing in-ground, in containers or in raised garden beds, the quality of your growing medium is arguably the most important factor in your quest for a thriving garden. The growing medium provides the necessary foundation for plant health, and must be able to support the nutrient needs, water needs and drainage needs required for plants to grow strong and robust. This means that before even starting a garden, our main focus should be on building up the soil, or preferred growing medium to be used, to ensure that it meets the necessary requirements for what is going to be grown.
There are many types of growing mediums available, each with their own advantages and disadvantages; depending on your location or climate, certain growing mediums may be more readily available than others. The right growing medium will provide optimum drainage for plant roots, efficient nutrient cycling and nutrient availability, while being able to hold an adequate amount of water to ensure plant roots are hydrated without being waterlogged.
Growing mediums also go well beyond just soil - there are a number of very effective soilless mediums that some growers use with much success. We will explore the various growing medium options below, listing the pros and cons associated with each one, allowing you to make an informed choice when starting your first garden.
Common Soil Based Growing Mediums
Topsoil
Probably the most commonly used growing medium for beginners is simple topsoil. This refers to the first few inches of ground soil that is readily available in our backyards. Top soil contains important organic matter, from fallen leaves and other plant materials that have been decomposed by the variety of microorganisms that are living within the ground.
While topsoil can definitely support plant growth, it is not always the most ideal growing medium as it can also contain weed seeds and other pathogens that can lead to plant disease. While it does contain nutrients, it may not have an adequate balance of what is needed to support your plants throughout all stages of life.
Store-bought topsoil may be slightly better than what is already in your backyard, as it has typically been filtered of larger debris and has an adequate structure that will provide aeration and drainage. However, even store-bought topsoil can contain low amount of nutrients and weed seeds that can become a nuisance in your garden during the growing season.
Loam
With an ideal texture and structure for holding moisture while allowing for adequate drainage, loam soil is a popular choice among gardeners. It contains a balanced amount of sand, silt and clay, as well as organic matter that allows for nutrients to be properly cycled and available for plant uptake. Loam is usually a high-quality soil that is rich in nutrients and works very well for the home garden.
The drawback of loam is that it can be expensive, and if you are filling large raised beds, this may make it inaccessible for some growers. The quality of loam soil can also greatly vary depending on where it is sourced from, and the cheaper brands may not have the right balance of organic materials.
Common Soilless Growing Mediums
Peat Moss
An popular growing medium for seed-starting, peat moss is naturally harvested from bogs primarily found in Canada and in Russia. Due to its sterile nature, peat moss is not vulnerable to common parasites or disease, which make it an excellent growing medium for establishing young plant roots. It boasts excellent water-retention, while remaining lightweight and has a slight acidity that can be beneficial for certain types of plants. It is also a low-cost option, but generally should be combined with other growing mediums for best results.
The disadvantage of growing in only peat moss is that nutrients may be limited and the acidic pH may not be beneficial for all types of growing. Balancing this growing medium out with Vermiculite or Compost can help to improve its aeration and better cycle nutrients. While peat is generally sustainable, as most harvesting is done while following strict environmental guidelines, there is also the possibility of sourcing peat that is harvested in a more destructive way.
It is important to know where the product is coming from and the standards that are being met during harvesting. Peat can also be used in smaller quantities, as an amendment that can add important structure and organic matter to a soil that is lacking in those things.
Coco Coir
Coco coir substrate is often pushed as an alternative peat moss, as they share similar water-retention and drainage abilities. It is generally thought to be sustainable, as it is a waste product from the coconut industry and entirely natural to process and manufacture. Due to its neutral pH, it provides a balanced environment for plants and is also sterile and free of weed seeds.
In most cases, coco coir will need to be supplemented with nutrients, as it does not contain enough to sustain plants past their initial stages of growth as small seedlings. Depending on your location, coco coir can be pricey, and so mixing it with other growing mediums is often recommended.
Commonly sold as coco coir bricks, the coir must be properly soaked and broken up into a loamy texture before planting, otherwise it can become waterlogged.
Perlite
Often seen included in potting soil mixes, perlite is a white, lightweight and sterile growing medium that can be used for propagation and seed starting. It has a texture similar to styrofoam, but offers excellent aeration for early root development while also retaining some water. It is a popular growing medium for hydroponic systems, is easily accessible and reasonably-priced.
Perlite on its own will not contain or hold onto adequate nutrients needed for optimal plant growth. As such, it requires the addition of nutrients or needs to be mixed with another substrate that can keep nutrients near the plant root zone. Perlite can create dust when it becomes too dry, and this can be an irritant for certain growers.
Vermiculite
Some gardeners will use a coarse vermiculite as an addition to their soil mixes in order to provide more aeration and drainage for tender plant roots. Like other soilless growing mediums, it can also be used for seed starting and has better water retention than perlite. Vermiculite is a great option for plants that require a bit more moisture to grow. While there has been controversy in regards to vermiculite insulation and its association with possible asbestos, vermiculite growing medium is generally considered to be safe when supplied from a trusted source.
Its disadvantages are that it may be slightly less effective when it comes to drainage, sometimes holding onto more water than necessary. It also tends to slowly break down over time and eventually may need to be replenished or mixed with another growing medium.
Organic Growing Mediums
Compost
While it may seem surprising, pure compost can be used on its own as an extremely effective growing medium. It is a nutrient-rich substrate with excellent structure, that provides optimum drainage and aeration, while promoting healthy microbial activity to ensure that nutrients are readily available for plant uptake. In a fabric planter growing system, like GardenSoxx, compost is actually one of the recommended options as it contains all the nutrition that plants need to grow healthy and vigorous. The main consideration that must be made is to ensure that the compost is fully decomposed, and does not contain any weed seeds or has not been compromised by any pathogens.
Provided your compost comes from a reputable source, or better yet, is your own homemade mixture that you have had full control over - it is safe to use and can be highly effective for a thriving garden. Compost can also be mixed in with other growing mediums to improve their structure, organic matter content and nutrient availability.
Worm Castings
While you may not want to just use them on their own, worm castings can be a highly effective addition to any existing growing medium as they are extremely nutrient-dense and give a significant boost to beneficial microbes. Worm castings can also improve soil structure, and can significantly increase yield and overall plant health.
Worm castings can be expensive when purchased in large quantities. Thankfully, even just a small amount of worm castings can go quite a long way in the garden. So adding them to your growing medium of choice is a great option to boost your garden health.
Choosing the right growing medium for your garden needs
To make an informed choice for your garden growing medium, you will need to consider the types of plants that you will be growing. For a herb and vegetable garden, it is best to choose a growing medium that is nutrient-rich, and allows for moisture-retention while also providing aeration and drainage. The key here is using a growing medium that provides a balanced structure and can also be amended over time when needed, to ensure it can continue supporting plant health. Growing other plants like succulents or other types of ornamentals may require a different balance of nutrients, drainage needs or specific soil pH levels.
Other factors to consider are the climate you are growing in and weather patterns that can affect plant growth and water levels in the soil. In hotter climates with little rain, choose a growing medium that holds onto moisture to ensure plants do not get dried out. In areas with more precipitation, a growing medium with optimal drainage is key.
When growing in large raised beds, the cost of high-quality growing mediums can be a major factor that can quickly add up. Some gardeners will fill the bottom of the raised beds with chopped up wood logs, or another bulky organic material to reduce the amount of actual growing medium needed to fill the raised bed to the top.
If there is already workable soil in the area being used for a garden, doing a soil test before planting is a great way to know what you are working with. Adding a top dressing of quality compost, worm castings or other quality growing medium can quickly transform a pile of “dirt” into an ideal area for a thriving garden!
Why quality matters MOST when choosing a growing medium
Starting with a high-quality growing medium in your garden is comparable to building a home on a strong and well-structured foundation. When care is put into the foundation of a home, there is less need to put more time and money into making changes over time. Quality growing mediums will lead to stronger plant root systems, which ultimately lead to healthier plants that produce a higher and more nutritious yield. When plants are healthy, there is also much less need to worry about plant disease or pest problems.
At the end of each season, plants can be cut at their base, leaving the healthy root systems in the soil to break down over time, adding back important organic matter that will continue to feed microbes and replenish the soil for the following growing season. Some growers also choose to plant cover crops during the off-season, to keep soil protected and keep soil microbiology active.
The right growing medium will offer the ideal balance between water retention and proper drainage, which will greatly reduce watering needs and allow for proper airflow to bring much-needed oxygen to developing root systems. A quality growing medium that produces healthy, resilient plants will actually continue to improve over time, as the active microbiology in the soil allows it to regenerate through the natural cycle of life.
The choice is yours, and will depend on what is available in your region, as well as what your budget and garden plan allow for. Keep in mind that combining more than one type of growing medium is also a very effective option that can help to cut costs while still providing optimal growing conditions for your crops.
