The Breakdown of Soil

There are two categories of soil or mediums: garden soil and potting soil. Garden soils are for use in gardens or lawns and potting soils are for use in pots or containers. While both may contain similar or overlapping ingredients, they are formulated for two very different purposes and should not be used interchangeably. Within the two types, there are numerous brands and blends that you can choose, each with different specific uses and varying qualities.

Potting soil is typically a mixture of peat moss, perlite, and humus, plus any additives necessary for the purpose of that specific blend. It usually contains an amendment for water retention and could contain a wetting agent to help disperse the water through the entire pot. It also includes a small quantity of fertilizer to provide some nutrient content for your plants. As potting soil has specialty ingredients, it is almost always more expensive than garden soil.

Garden soil is generally a high-quality topsoil, blended with amendments such as peat moss, sand, and compost, to improve the structure of your existing soil. It is usually pH-balanced and contains some nutrient value for your plants. The primary garden soil that is sold in Canada is referred to as triple mix.

In regard to quality, it may be tempting to pick a bargain option thinking all soil is the same. In reality, better brands will have a few different ways that they provide a better product:

1. Heat-treated to reduce or eliminate weed seeds and harmful microbes
2. Screened to remove any large debris
3. Higher nutrient content
4. Lower salt content
5. pH balanced
6. Additives like mycorrhizae to improve nutrient uptake by the plants
7. Better quality ingredients that are sustainably harvested

Typically in bargain soils, we see large wood chunks or debris, filler ingredients that provide no value to the plant, and poor salt or pH values that reduce the plant's ability to uptake nutrients.

All Purpose Potting Mix: A general, all-purpose mix for use in containers outdoors. Depending on the brand, they may vary in how much moisture they hold, so they may or may not be good for indoor use.

Vegetable Potting Mix: A peat moss-based mix with additives like compost, natural fertilizer, and coconut husk fibre. They are designed to hold moisture for full sun environments that veggies love, so they are not suitable for indoor use. Most quality brands are also certified for organic use.

Indoor Potting Mix: A combination of peat moss, black earth, a water-retention agent like perlite, vermiculite, or coco coir, and other additives. Formulated for houseplants in containers that prefer averagely to relatively moist soil.

Cactus and Succulent Potting Mix: A combination of peat moss, sand, an aeration agent like perlite, and other additives. It is a fast-draining soil medium for plants in containers that need to dry out quickly.

High Porosity Mix: A combination of peat moss and a high percentage of coarse perlite. It dries out more frequently than all-purpose potting mixes, making it ideal for low-light conditions or plants that prefer very well-draining soil.

Orchid Mix: These can be anything from bark, sphagnum moss, or a mixture of both with other additives. Generally, most orchid mixes will be very fast-draining and resist compaction so the roots are able to get air.

Seed-Starting Mix: A lightweight, well-draining medium that allows young seedlings to push through the soil with ease. It generally contains coconut fibre for water retention to ensure good germination.

Triple Mix: A combination of peat moss, compost, and topsoil. This is the soil we recommend for almost all planting projects in the garden, no matter the plant. It can also be used for top-dressing lawns if topsoil is not available.

Topsoil: The uppermost layer of soil, containing a decent amount of organic matter. A good topsoil will also be screened to remove any large pieces of debris. It is a great option for top-dressing lawns, levelling and filling holes, or laying sod. It can also be used as garden soil in a pinch, but is not enriched or amended at all so has limited value as a growing medium.

Black Earth: Typically composed of black peat, which is from the bottom of the peat bogs. It is incredibly dense and doesn't hold nutrient content as well as other options so it should not be used to backfill new plants with. While it can be used as a soil amendment, compost would be a better choice. It can also be used for over-seeding, but topsoil would be a better choice. We recommend it only for repairing holes, levelling the ground, laying sod, or similar projects.

To improve your soil quality, it is a great practice to add compost once a year, either early spring or late fall. This will add organic material and nutrients into your soil, improving it and your plants' health over time.

There are a few different compost types with different ingredients that you can choose from. Each has different benefits, depending on your existing soil and your goals. No matter which one you pick, our recommendation is to apply 1 bag (25-30L) per 10 square feet of garden once a year.

Composted Manure: Fully composted cattle manure mixed with peat that adds organic matter and microorganisms to improve soil structure, nutrient access, and water retention.

Woodland Compost (Biofor): Composted manure mixed with peat and bark, which is certified for organic use. It offers all the benefits of composted manure, plus the bark and wood fibre additive improves air and water circulation for optimal root growth, making this a fantastic option for breaking up clay soil.

Sea Compost (Biosol): Composted manure mixed with peat, seaweed & crustaceans, which is certified for organic use. It offers all the benefits of composted manure, while the seaweed and crustaceans add a source of trace nutrients necessary for plant growth. The nutrient value of this compost is higher than the other options, feeding your plants for strong, healthy growth.

Both potting soil and garden soil are blends with combinations of ingredients. All of these ingredients contribute to the medium’s effectiveness in a different way and, by working together, they promote a healthy root system and a healthy plant. Below are some of the common components that you will encounter and their intended purpose. Some of these ingredients can also be purchased individually to amend or create your own potting soil.

Bark: Bark can be found both individually as an orchid-growing medium or as an additive in a soil mix. It helps improve drainage and aeration by creating air pockets in the soil.

Coconut Husk Fibre/Coco Coir: Shredded coconut husk that is also used for water retention and aeration, so it can be used as an alternative to peat moss in mixes.

Compost: Decayed organic material, ranging from seaweed and kelp to barnyard manure to woodland bark. It is added to soils to improve the soil structure while increasing the amount of nutrients in the soil for the plant to uptake.

Dolomitic Limestone: A combination of calcium carbonate and magnesium carbonate. It is used to reduce soil acidity and provides a source of magnesium and calcium for the plant. It is often paired with peat moss to balance the pH of the medium.

Humus or Black Earth: A dark, organic material that is left after plant material and animal remains decay.

Peat Moss: Peat moss comes from dead and decaying sphagnum moss that is found at the bottom of bogs, and can contain other organic material mixed in. It can be soil individually in compressed bales or it can be an amendment in many potting and garden soils. It does not contain any nutrient content, so it is normally accompanied by a fertilizer of sorts. Peat moss has a high water retention rate and does not compact, providing good aeration for the roots.

Perlite: A volcanic glass that has been heated until it ‘pops’ and expands, producing a lightweight, porous material called perlite. When added to a mix, it improves drainage and aeration by creating air pockets in soil, lightens heavy soils, and helps prevent soil compaction. It can also be used on its own for starting cuttings or seeds.

Sand: Used to increase soil drainage.

Sphagnum Moss: A plant that grows on top of bogs throughout Canada, New Zealand, Ireland, and more. It is harvested, dried, and sterilized before being packaged for sale. On its own, it can be used as an orchid or carnivorous medium, or for starting cuttings and seeds. When added to a potting medium, it increases water retention.

Vermiculite: An aluminum-iron-magnesium silicate that is also heated until it expands. Once expanded, vermiculite can absorb up to 4 times its weight in water. This makes it an ideal soil amendment for those looking to significantly increase moisture retention in their potting mix. Its primary use, however, is to retain moisture for starting certain seeds by adding a layer on top of your plant medium.

Wetting Agent: A chemical compound that reduces the surface tension of water, allowing it to penetrate and absorb into the soil more easily and more thoroughly.

Worm Castings: The waste that earthworms produce after they have digested the organic matter in soil. It is used as an organic fertilizer as it contains helpful nutrients and enzymes for plants, as well as improving soil structure.