Potting Soil vs Potting Mix: Which Is Best?

Potting soil and potting mix are both common growing mediums for potted plants, but they are not interchangeable. 

Potting soil is primarily composed of soil, while potting mix is a blend of organic materials. Each option has its own benefits and drawbacks, and choosing the right one can make a significant difference in the health and growth of your plants.

But, there’s more to it than just soil or organic material. Did you know that the composition of your potting mix or soil can impact the environment and even your wallet? 

In this article, I’ll dive deeper into the differences between potting soil and potting mix, and explore the potential environmental concerns and cost considerations associated with each option. 

So, if you’re looking to optimize your potted plant growth while also being mindful of the environment and your wallet, keep reading to learn more!

Potting soil vs potting mix: What’s the difference?

Potting soil is typically made from soil and organic matter, such as peat moss or composted bark. Meanwhile, potting mix is a soilless growing medium that’s made from a combination of organic and inorganic materials, such as peat moss, vermiculite, perlite, and coconut coir.

Potting soil and potting mix are two types of growing media that are commonly used in gardening and indoor plant care. Although they may seem similar, there are some significant differences between the two that gardeners should be aware of.

In the case of potting soil, it may also include inorganic materials like sand or perlite, which help to improve the texture and drainage. Potting soil is often used in outdoor gardening, such as in planting beds, where plants can benefit from the natural properties of soil.

The goal of potting mix, on the other hand, is to be lightweight, well-draining, and sterile, which makes potting mix ideal for indoor plants or container gardening, where good drainage and aeration are crucial to avoid root rot.

One of the primary differences between potting soil and potting mix is the composition. Potting soil contains soil, which means it can have varying textures and nutrient content depending on the soil source. 

This can make it more challenging to maintain consistent growing conditions for plants, particularly in indoor settings. On the other hand, potting mix is a more uniform and consistent growing medium, which makes it easier to manage the growing environment.

Another key difference is the moisture retention properties. Potting soil tends to hold onto moisture for longer periods, which can be beneficial for plants in hot, dry climates. 

However, in humid or wet environments, potting soil can become waterlogged and lead to root rot. In contrast, potting mix is designed to be well-draining and porous, which helps to prevent waterlogging and promote healthy root growth.

Lastly, potting soil and potting mix may differ in nutrient content. Potting soil may contain various nutrients from the soil, depending on its source and quality. However, these nutrients may not be consistent or easily accessible to plants. 

Potting mix, on the other hand, is often formulated with added nutrients, such as fertilizers or organic matter, which can help to support plant growth.

When might you use potting soil instead of potting mix?

While potting mix is generally considered the best choice for indoor plants or container gardening, there are some situations where potting soil may be a better option. For instance, some plants require a higher pH level than what’s typically found in potting mix. 

If you’re growing cactus or succulents, for example, they tend to prefer a higher pH level, so potting soil may be a better choice for these types of plants.

Another scenario where potting soil is a good option is for outdoor gardening. Potting soil is better suited for planting in the ground, as it contains actual soil that provides the necessary nutrients and structure for plants to grow. 

Additionally, using potting mix for outdoor planting can be expensive, as it’s often more costly than potting soil due to the materials used to make it.

If you’re on a budget, potting soil might be the way to go for indoor plants too. While it may not be as consistent or uniform as potting mix, it can still provide a suitable growing medium for many plants, especially those that are less picky in terms of soil moisture or nutrient needs.

Lastly, some gardeners prefer to make their own potting soil instead of buying pre-made potting mix. Homemade potting soil can be created by mixing soil, organic matter like compost or peat moss, and other additives like sand or perlite. 

While it may require more effort than simply buying a pre-made potting mix, making your own potting soil can give you more control over the composition of the medium and allow you to tailor it to the specific needs of your plants.

Should I use potting mix or potting soil for indoor plants?

In general, potting mix is the better choice for indoor plants due to its well-draining properties, added nutrients, and sterility. However, there may be some situations where potting soil is preferred, such as for plants that require a higher pH level or for gardeners on a budget.

There are some key reasons though why, if you can, try to go for potting mix.

First off, drainage is critical for indoor plants because they’re more susceptible to root rot. Potting mix is designed to be well-draining and porous, which allows for better aeration and helps prevent over-watering. 

On the other hand, potting soil can hold onto moisture for longer periods, increasing the risk of root rot.

Another factor to consider is nutrient content. While potting soil may contain some nutrients, potting mix is typically formulated with added nutrients like fertilizers or organic matter to support plant growth.

Sterility is also important for indoor plants, as they can be more susceptible to pests and diseases. Using a sterile growing medium like potting mix can help reduce the risk of plant health issues.

Some indoor plants also prefer a specific pH level in their growing medium. Potting soil may have a higher pH level than potting mix, making it a better choice for plants that prefer a more alkaline soil.

Lastly, potting mix is generally more consistent in its composition, which makes it easier to manage the growing environment and provides more consistent growing conditions for plants.

Is potting soil just dirt?

No, potting soil is not just dirt. While the name might suggest that it’s just regular soil used for planting in containers, potting soil is actually a mixture of different materials that provide a suitable growing medium for plants.

Although some potting soils may contain actual soil, they typically include other organic materials like peat moss, composted bark, or coconut coir, as well as inorganic materials like perlite or vermiculite. 

The purpose of these different materials is to create a lightweight, well-draining, and nutrient-rich growing medium for plants.

The specific composition of potting soil can vary depending on the manufacturer and the intended use. Some potting soils may have a higher proportion of soil, while others may be formulated with more organic or inorganic materials depending on the desired growing conditions.

Why do we use potting mix and other non soil substrates rather than soil in containers?

Improved drainage is a key advantage of non-soil substrates. Excess water can accumulate in containers, leading to root rot and other issues. Potting mix and other non-soil substrates are specifically designed to be well-draining, which helps prevent water buildup and promotes healthy root development.

Another benefit is sterility. Regular soil can contain harmful bacteria, fungi, and other microorganisms that can cause plant health issues. Non-soil substrates are often sterilized before use, which reduces the risk of plant diseases.

Consistency is also important in container gardening. Non-soil substrates are typically more uniform in terms of their composition and nutrient content than regular soil, which provides a more stable growing environment for plants.

In addition, non-soil substrates can be specifically formulated with added nutrients, like fertilizers or organic matter, to support plant growth. This is especially important in containers, where plants have limited access to nutrients in the surrounding environment.

Lastly, non-soil substrates are typically lighter and easier to work with than regular soil, which can be especially important in container gardening.

Can you use garden soil instead of potting soil for potted plants?

It’s not a good idea to use garden soil instead of potting soil for potted plants. One main reason is that garden soil can be dense and heavy, which can impede drainage in potted plants. This can lead to water buildup, which can cause root rot and other plant health issues.

Another potential issue is nutrient availability. Garden soil may not have the necessary nutrients required for potted plants to thrive. 

Potted plants are confined to a small space though and may not have access to nutrients in the surrounding environment, so it’s important to provide a nutrient-rich growing medium.

Pests, disease-causing organisms, and weed seeds are also a concern when using garden soil in potted plants. Garden soil can introduce soil-borne diseases that can be difficult to control, and pests like slugs and snails can quickly become a problem.

The pH level of garden soil can also be different from potting soil, which can affect the ability of plants to absorb nutrients. Potted plants may require a specific pH level for optimal growth, so it’s important to use a growing medium that is tailored to their specific needs.

Lastly, the texture of garden soil may not be suitable for potted plants. Potting soil is typically formulated with lightweight and porous materials like peat moss, vermiculite, or perlite to provide a well-draining and aerated growing medium.

Does potting soil contain nutrients or do I need to add fertilizers?

Potting soil does contain nutrients, although the exact composition can vary depending on the type and brand. Typically, most potting soils will have a basic mix of macronutrients like nitrogen, phosphorus, and potassium, as well as micronutrients such as calcium, magnesium, and iron.

However, it’s important to note that nutrients in potting soil can become depleted over time, especially as plants absorb them. Therefore, it’s recommended to regularly fertilize potted plants to ensure they have access to the nutrients they need for healthy growth.

Related: How to Add Calcium to Soil (for Optimal Plant Growth)

There are different types of fertilizers that can be used for potted plants. Organic fertilizers, such as compost or worm castings, are a popular choice as they provide slow-release nutrients and can improve soil health over time. 

Chemical fertilizers are also an option, but it’s important to follow the manufacturer’s instructions carefully to avoid over-fertilizing, which can harm the plants.

It’s also worth mentioning that some potting soils are formulated with added fertilizers, while others may not contain as many nutrients. When selecting a potting soil, it’s important to read the label and choose one that meets the specific needs of the plants you are growing.

Is potting mix more expensive than potting soil?

The cost of potting mix and potting soil can vary depending on factors such as brand, quality, and location. Generally, potting mix tends to be more expensive than potting soil. The reason for this is that potting mix is made from a blend of materials such as peat moss, vermiculite, perlite, coconut coir, and composted bark.

These are typically more expensive than the materials used in potting soil, such as sand, clay, and topsoil. In addition, the manufacturing process for potting mix can be more complex, involving sterilization, pH level adjustments, and added fertilizers, which can increase the cost of production.

However, it’s important to note that not all potting mixes are equally expensive. Some brands may use lower-quality materials or have fewer added nutrients, which can result in a lower cost.

Potting soil, on the other hand, is often less expensive due to the lower cost of materials and simpler manufacturing process. However, like potting mix, the cost can vary depending on the brand and quality.

It’s important to invest in quality soil or mix, regardless of the cost. Doing so can pay off in the long run by promoting healthy plant growth and reducing the need for additional fertilizers or soil amendments.

Can I make my own potting soil or potting mix?

You can absolutely make your own potting soil or potting mix using a variety of materials. This is a great way to save money and customize the composition to suit your specific plant needs. Some common materials used in homemade potting soil mixes include compost, perlite, vermiculite, coconut coir, sand, and peat moss. 

Depending on the specific needs of your plants, you can adjust the mix to improve drainage, water retention, and aeration.

When creating your own mix, it’s important to consider the sterilization of materials to avoid introducing harmful bacteria or fungus to your plants. You can sterilize the soil or compost by baking it at 180-200 degrees Fahrenheit for 30 minutes.

While making your own potting mix can be cost-effective and customizable, it’s important to note that it may not always be a perfect substitute for store-bought mixes. Store-bought mixes often have specific nutrient compositions and pH levels that may be difficult to replicate at home.

Ultimately, making your own potting soil or mix can be a great option for those who want more control over the composition of their growing medium. Just be sure to research the specific needs of your plants and sterilize materials to ensure healthy growth.

Environmental concerns with using potting soil vs potting mix

There are several environmental concerns associated with using potting soil and potting mix that gardeners should be aware of. One major issue is the use of peat moss, which is often harvested from wetlands. This process can cause environmental damage and contribute to the release of greenhouse gases, while also depleting a non-renewable resource. 

To reduce this impact, gardeners can choose sustainable alternatives such as coconut coir.

Another concern is the use of synthetic fertilizers and pesticides, which can be harmful to the environment and contribute to soil and water pollution. Organic alternatives like compost and worm castings can be used instead.

The manufacturing process of potting soil and mix can also be energy-intensive, leading to greenhouse gas emissions. Gardeners can reduce this impact by choosing locally sourced products and by using renewable energy sources in production.

Finally, the disposal of used soil can also pose environmental challenges. Gardeners should properly dispose of used soil to prevent the spread of pests, disease, or weed seeds. Sustainable alternatives like vermiculture or composting can also be used.