Potting Soil vs Garden Soil | Understanding the differences!

When it comes to growing plants, indoors or outdoors, few aspects are as important as the choice of growing media. Unless your garden relies fully on hydroponics, you will probably have to choose between potting soil and garden soil at some point. So, what is the difference between these two soil types, and which one is the best for your plants? This guide will help you answer these questions as well as go over the different subtypes of the two varieties.

What is Potting Soil?

Potting soil is also commonly known as potting mix and is made from a blend of materials intended for growing plants in pots or other containers. The most common materials in this blend include coir, compost, vermiculite, perlite, bark, and sphagnum moss. Yes, the blend does not have soil despite being known as potting soil. The primary reason for excluding soil in this mix is to prevent infections resulting from plant pathogens and fungi present in the soil.

The organic materials in the blend (moss or compost) provide nutrients to the plants, while the perlite or vermiculite enhances drainage by keeping the potting mix loose. This results in a well-drained potting mix that enhances breathability and root health. Additionally, some potting soil varieties contain water-retention crystals and chemical fertilizers. These mixes are available in major online stores and can be ordered for specific plant types such as succulents, roses, orchids, or seeds.

Despite the obvious lack of soil, potting mixes are excellent growth media for herbs, vegetables, flowers, and other plant types. Remember that different manufacturers might have slightly varied usage directions regarding their product, so be careful to follow the instruction label after purchase.

What is Garden Soil?

Garden soil is essentially topsoil that has been enriched with organic matter such as compost so that it’s more nutritious for plants. It’s heavier in texture than conventional soil and thus retains water better than potting soil or regular soil. Price-wise, garden soil is considerably cheaper than potting soil due to the absence of pricey ingredients such as perlite or vermiculite. Still, garden soil has some premium feel to it since it’s sold in packaged and often labeled bags. Keep in mind that the exact enrichment content varies from one supplier to another.

There are numerous garden soil varieties available in today’s market. The variant you choose depends largely on the plants you intend to plant on the soil. If you browse the garden soil section on most stores, you will most probably come across labels such as ‘garden soil for shrubs,’ ‘garden soil for vegetables,’ or even ‘garden soil for trees.’ While the content does not vary too much, it is advisable to get the soil best suited for your plants.

What are the Differences Between Garden Soil And Potting Soil?

Here is a look at the main differences [1] between these two common soil varieties.

• Composition: As the names suggest, garden soil contains naturally occurring soil enriched with organic materials to become more nutritious. Typically, garden soil contains plant matter, composite, natural rocks, loam, silt, and sand. On the other hand, potting soil is intended for potted plants and contains coir, compost, vermiculite, perlite, bark, and sphagnum moss.
• Categorization: Potting soils are categorized based on the materials used in the blend. Garden soil, on the other hand, is classified according to the dominant component. Loam garden soil has a lot of loamy soil, while clay garden soil has a lot of clay soil in the component mix.
• Microbe presence: Potting soil is free of microbes and is often referred to as a non-living medium. Garden soil is a living medium and provides a conducive environment for living things such as nematodes, fungi, and bacteria to thrive.
• Water retention: Garden soil is better suited for outdoor use since it drains water easily and can be watered using regular metal, rubber, or expandable hose pipes. Potting soil retains water better and is more suited for indoor gardens. Potting mixes are best watered using a watering can.
• Texture: The constituent ingredients usually determine soil texture. In this case, garden soil tends to be significantly heavier than potting soil. The light texture associated with potting mixes makes them extremely easy to work with.
• Processing: Potting soil is usually made up of processed components such as perlite, vermiculite, or bark. This processing leaves very few, if any, microbes alive. The manufacturers of potting mixes intentionally sterilize the blends to kill weeds and eliminate any potentially harmful microbes. While the resulting mix is significantly safe for plants, the absence of beneficial microbes affects the plants’ nutrition uptake. On the other hand, garden soil is usually minimally processed and thus has a rich mix of nematodes, actinomycetes, fungi, protozoa, and bacteria. Some of these are beneficial, while others are not.
• Risk to plants and humans: Potting mixes are virtually harmless to plants and humans. This attribute is the result of stringent processing that eliminates most, if not all, living components. The same cannot be said for garden soil which contains numerous microorganisms, some potentially harmful to people and plants.
• Price: Potting soil is considerably more expensive to buy compared to garden soil. The presence of pricey ingredients such as perlite, coir, and vermiculite drives up the price significantly.

When to Use Garden Soil?

Here is a look at instances in which garden soil would be the superior choice compared to a potting mix.

When You Have an Outdoor Garden

If your gardening project is primarily located outdoors, using garden soil will be far more economical than using potting mix. One of the reasons for this is the costs involved. Purchasing sufficient potting mix for an outdoor garden could become quite expensive, even in the short run. Additionally, if your garden is made up of plants that can only thrive outdoors and with deep root systems, potting mix is no longer a choice for you.

When You Need Renewable Soil

Renewing soil means adding components to the soil to make it better-textured, more nutrient-rich, or easier to work with. With garden soil, you can always add compost material or any other organic substances to improve the soil’s quality. With the potting mix, renewal is somewhat complicated due to the nature of materials used in the initial formulation.

When Starting Vegetables on a Seed Bed

Starting vegetables outdoors requires one to have a seedbed, preferably slightly raised. To do this, you will need a significant amount of growth media, something that might be quite tricky when using potting mixes. Additionally, garden soil is extremely easy to adjust in terms of acidity and alkalinity, making it ideal for vegetable nurseries. Unlike potting soil, you can easily enrich garden soil by adding manure or compost. The resulting soil often has better soil structure, porosity, and nutrient content.

Keep in mind that garden soil is unsuitable for use in containers. This is due to the lack of pumice, perlite, vermiculite, or any other drainage-enhancing component. When used as a potting medium, garden soil can easily result in water logging or plant diseases related to excessive moisture.

When to Use Potting Soil?

Despite being significantly pricier than garden soil, there are instances where potting mixes are preferable to garden soil. Here is a brief look.

When Outdoor Gardens Have Fungal Infections

Sometimes, farming outdoors might not be very conducive, depending on the state of the soil. For example, your outdoor space might have a prevalent fungi infection making it unsuitable for gardening. In such a case, you would be better off having several indoor gardening containers and utilize potting mixes as the growth media.

Additionally, you might also prefer using potting soil when dealing with plants that are overly susceptible to soil-borne diseases.

When Your Plants Are Not Resistant to Overwatering

Potting mixes contain perlite or vermiculite that vastly enhance drainage. Compared to garden soil or regular soil, potting mixes have excellent drainage and breathability. If the plants you intend to have in your garden are easily susceptible to excessive moisture or water, then you would be better off planting them in potting soil.

When Your Plants Require Potting Mixes

Some plants thrive under the conditions created by a potting mix. While such plants will still grow in regular or garden soil, they might struggle to reach maturity, flower, or produce fruit. For example, most garden stores have potting mixes made specifically for cacti growth. The target plants, in such a case, perform exceptionally well when planted on the potting mix.

If You Find Garden Soil Too Difficult to Work With

Potting soil has an extremely light texture, making it ideal for working with most beginner and enthusiast gardeners. Garden soil, particularly the clay or loamy variety, can be quite tricky to work with due to the heavy texture. It is also worth noting that potting mixes are designed to be used straight out of the box, unlike garden soil that may require some minor adjustments.

When You Are Considering Soilless Farming

While using a potting mix is nowhere close to using hydroponics, it is still a step on the path to soilless farming. If you have been considering a switch to hydroponics, starting with potting mixes will give you a slight idea of what to expect with soilless farming.

Keep in mind that using potting soil on a large scale can be quite expensive, worth noting if you are on a budget. Additionally, some mixes are unsuitable for organic farming due to the synthetic material content. The significantly low nutritional value of potting mixes also makes them unsuitable for perennial plants.

Types of Potting Soil

Here is a look at the common types of potting soil [2].

Orchid Potting Soil

Orchids are arguably some of the most demanding plants when it comes to drainage and air circulation. Orchid potting mix is specially formulated to provide unrivaled aeration and drainage to enhance sensitive orchids’ growth.

Organic Potting Soil

As mentioned earlier, some potting mixes are unsuitable for organic farming due to the presence of synthetic components. Organic potting soil is formulated to address this problem. The entire mix is made from organic plant and animal-based materials, including bones, manures, food compost, and worm castings. Organic potting is among the most fertile variants of potting mixes.

Moisture Control Potting Soil

As the name suggests, this mix contains moisture-control pellets that prevent the soil from drying out completely. This control gives the plant ample time to absorb as much moisture as it requires from the soil.

Seed Starting Mix

This is a super fine blend of potting soil designed to provide perfect conditions for germination. Keep in mind that seed starting mixes are quite low in nutritional value. This deficiency encourages root growth by spurring the plant roots to branch out in search of nutrients.

Citrus and Cacti Potting Soil

Cacti and citrus fruits also thrive in well-drained soil. In this potting mix, the manufacturer adds some sand to make the entire mixture better aerated and well-draining.

All Purpose Potting Soil

This is probably the most common potting soil variant. It is ideal for growing indoor and outdoor plants in containers. Designed without any specific plant type in mind, the all-purpose mix works well for many plants. If you are unsure of the mix to purchase, you will probably not go wrong with this one.

Outdoor Potting Mix

Outdoor potting mixes are designed to mimic a forest environment. This soil often contains higher fertilizer compositions, and at times, moisture-retention pellets. However, the mix is still fully usable in an indoor garden.

Types of Garden Soil

Garden soil is usually categorized based on the dominant soil type [3]. Here is a brief look.

Loam Soil

Loam soil is the perfect balance between clay, silt, and sandy soils. The soil has the advantages associated with each of the component soils and almost none of the drawbacks. Loamy soil is typically fertile and quite easy to work with. Depending on the dominant composition, loam soil can either lean towards clay or sandy soil. Since loam is considered perfectly balanced soil, it is a beginner gardener’s best friend. Still, the soil can be improved by adding some organic matter.

Clay Soil

Clay soil has an extremely heavy texture but also tends to be nutrient-laden. Clay soil dries out gradually at room temperatures and remains wet in cold temperatures. Due to the extremely small spaces found between particles in clay soil, it can hold water for significantly longer than any other soil type. Despite the nutritional value, though, clay soil can be quite tasking for a gardener due to its heavy texture. Additionally, the soil is unsuitable for plants that only thrive in well-drained soils.

Silt Soil

Silt soil is renowned for its high fertility, moisture-retention, and light texture. This soil is made up of medium-sized particles that hold moisture but still have great drainage. Silt soil can be easily washed away by rain and often requires the addition of organic matter to compact it to the desired level.

Sandy Soil

Sandy soil is low in nutrients, slightly acidic, dry, warm, and light in texture. When sandy soil is the main component of garden soil, the resulting texture is significantly lighter than one in which clay soil is the main component. Sandy soil is extremely easy to work with and has outstanding drainage. This soil variant warms up quite quickly but easily dries up under high temperatures. Garden soil made predominantly with sandy soil needs a significant nutrient boost using composite materials.

Peat Soil

Peat soil is among the rarest types of garden soil. However, you can order some to add to your garden to improve fertility, moisture retention, and drainage. Peat soil has extremely high levels of organic matter that is quite beneficial to any plant.

Chalk Soil

Chalk soil can come in a light or heavy texture but is always alkaline as a result of the high calcium carbonate content. This soil is highly unsuitable for plants that only thrive in acidic environments. However, if this is the only soil type available, it can always be acidified to accommodate ericaceous plants’ growth.

Summary

Every modern gardener is bound to come across the potting soil/garden soil debate at some point. Each variant has its unique pros and cons and instances best suited to the use of each. Hopefully, the information in this article will lead you to a well-informed choice when it comes to selecting a growth medium for your indoor or outdoor garden.

Citations

1. https://treillageonline.com/potting-soil-vs-garden-soil/
2. https://harpersnurseries.com/potting-soil-types/
3. https://www.boughton.co.uk/products/topsoils/soil-types/