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Topsoil vs. Potting Soil: Differences + Potting Mix Explained

Topsoil vs. Potting Soil: Differences + Potting Mix Explained

Understanding the difference between Top Soil and Potting Soil is crucial for successful gardening, as it impacts plant growth, moisture control, and the overall wellbeing of the garden. While topsoil is typically used for outdoor landscaping, it differs greatly from potting soil, which is specifically formulated for plants in containers. (Source)

Topsoil is basic, unenriched soil for outdoor use, while potting soil is enriched, promoting better plant growth and moisture management in container plants.

This article will guide you through these differences and offer practical tips for optimizing the use and improvement of both topsoil and garden beds, especially relevant for gardeners in greenhouses and similar settings. (Source)

Key Takeaways: Topsoil vs. Potting Soil

  • Topsoil vs Potting Soil: Topsoil is the upper layer of earth, ideal for large outdoor areas and landscaping, whereas potting soil is enriched and designed for container gardening, offering better plant growth and moisture control.
  • Topsoil Uses: Best used for filling large areas, building flower beds, and repairing yard damage. Can be improved by addressing soil compaction, microbial life, and chemical input reduction.
  • Potting Soil Benefits: Ideal for indoor and outdoor container plants, potting soil provides essential nutrients and drainage. It’s lighter and less likely to compact than topsoil, making it better for plant containers.

What Is Topsoil? 

A pile of fresh topsoil in a driveway of a well-manicured yard.

Before we continue, you need to know that topsoil is not the same as garden soil.  (Read more about the differences between topsoil and garden soil.)

Topsoil is the uppermost layer of the earth’s soil, characterized by a high concentration of organic matter and nutrients, essential for plant growth. It’s where plant roots mostly exist, playing a vital role in soil fertility and soil structure.

This layer is significant in gardening and agriculture, as it supports the development of a wide range of plants, from grasses to trees. Topsoil is also often enriched or amended to further enhance its quality for specific gardening needs.

Using Topsoil: Key Gardening Uses

Topsoil is commonly used for various large-scale gardening and landscaping projects due to its composition and availability. Its primary uses include filling in areas like old ponds, building substantial flower beds and borders, repairing yard damage caused by erosion, and revitalizing unhealthy gardens.

While it’s suitable for these extensive applications, topsoil is generally not used for more focused or small-scale tasks, such as planting seedlings, where more specialized garden soils are preferred.

What Potting Soil? 

Potting soil is a special mix made for growing plants in containers. It’s rich in nutrients and has ingredients like vermiculite and sand to help with soil aeration and water retention. This soil is perfect for container plants, providing the right amount of moisture, fertility, and porosity for healthy plant growth. It’s different from regular garden soil because it’s made to support plants in smaller, contained spaces.

Potting Soil Uses

Potting soil is suitable for growing plants both indoors and outdoors, offering versatility for various planting needs. For container gardening, a specialized version known as potting mix is recommended. This mix is lighter and drains better than regular potting soil, ensuring that plants thrive in pots just as well as they would in natural ground soil.

Topic Details
Potting Soil Uses Suitable for indoor and outdoor plants. A premium version, known as potting mix, is better for container gardening due to improved drainage and less compaction.
Why Use Potting Soil In regular gardening, soil teems with beneficial microorganisms. For potted plants, potting soil provides necessary nutrition and drainage, compensating for the absence of natural microbial networks.
Container Gardening Focuses on precise nutrient balance and drainage, key for plant health in pots, as they miss out on ground soil’s natural benefits.

Potting soil is crucial for providing an optimal growing environment in container gardening. In natural garden soil, microscopic life such as bacteria and fungi form a balanced ecosystem, protecting plants from pests and diseases and making the soil resilient to climate extremes.

For potted plants, focusing on nutrition and drainage is vital because they lack natural microbial networks. Good potting soil compensates for this absence, supplying necessary nutrients and ensuring proper drainage to support healthy plant growth in confined spaces.

What’s the Difference Between Potting Soil and Potting Mix? 

People often confuse potting soil with potting mix.

Potting soil is denser and heavier. It isn’t sterile, so it could have some pests present. Due to its texture, potting soil is more likely to get compacted than potting mix. Potting soil would be great for large outdoor pots in which you’re growing vegetables. But for house plants, I’d recommend going for a lighter potting mix. 

How To Decide Which Soil To Use

If the plants you are growing are native to dry environments, you want a potting mix rather than potting soil, but for most plants, you’ll be okay with potting soil so long as you don’t overwater it. 

Topsoil would be for covering large areas; you definitely don’t want potting mix for that! 
This is an additional read If you want to know more about Miracle-Gro Potting Mix.

How to make a good potting mix

Amanda suggests a mixture of 60% coconut coir and 40% drainage and nutrients made up of pumice and worm castings.

(You could use peat moss instead of coconut coir, but here is why I don’t). 

Types of Soil & Improvement: What Else Should You Know?

Now that we’ve covered the main differences and uses of various soils, it’s time to dig deeper into gardening soil specifics. This will help you achieve the best results, whether you’re working on container plants, enhancing fertility in garden beds, or aiming for optimal plant growth and moisture management in your greenhouse.

How To Improve Topsoil

Improving topsoil is essential when you notice that your plants are not thriving as expected, indicating that the soil may lack necessary nutrients or proper structure. Whether it’s a new garden area stripped of its natural soil by construction or an existing garden bed that’s underperforming, enhancing your topsoil can significantly boost plant health and growth.

Sometimes it is appropriate to buy topsoil. For example, if you’ve just built a new house and heavy machinery has removed all the soil around the building, then you might want to buy a truckload to speed up the recovery process. 

But if your existing topsoil is just not working well for your plants, then you can improve it.

First, you’d need to work out what type of soil you have. Loam soil is highly desired by gardeners, but it’s also possible to improve sandy soil or clay soil with the right management. 

If your soil texture seems fine, there are a couple of other things that might be the problem. Usually, these would be:

  • Compaction 
  • Not enough microbial life 
  • Overuse of fertilizers or pesticides 

Explaining how to fully address these issues is complex, but these top tips can start you on the path to improving topsoil:

Fixing Compaction 

  • Don’t drive vehicles on your lawn 
  • Don’t leave any bare soil (rainfall on uncovered ground is a significant cause of compaction.)
  • Don’t use a cultivator, tiller, or rotavator (sorry, but it’s not worth it!)

Encouraging Microbial Life

  • Consider no-dig gardening (this book covers it all)
  • Avoid using fungicides or pesticides as they can harm beneficial organisms as well as pests.
  • Leave the grass cuttings on the lawn to feed the soil 

Reducing Chemical Inputs 

  • Consider organic fertilizers instead of chemical ones
  • If necessary, consider biological controls for pests 
  • Compost and worm castings are your friends!

Types of Potting Soil 

You can use potting soil or potting mix for growing plants in pots. Potting mix is more expensive, but it’s also better for growing in pots because it drains more effectively. Succulents would need more drainage than you get with general potting soil, so a good-quality potting mix will be even more important.

You can make potting soil from a whole mix of different ingredients. But generally speaking, you need three things:

  • Organic matter (e.g. coco coir)
  • Drainage materials (e.g. pumice)
  • Nutrients (e.g. worm castings)

Add horticultural charcoal to the pot’s bottom to prevent bad odors from house plants.
For suggestions on fertilizer-free potting soil, read this.

How To Improve Potting Soil

Improving potting soil is key when you find that your container plants are not growing as robustly as they should. This often means the potting soil has lost nutrients or its structure, affecting water retention and airflow.

Here is what you can do to improve potting soil:

  • Add Compost: Mix in well-rotted compost to replenish organic matter and nutrients.
  • Incorporate Fertilizer: Use a balanced fertilizer to provide essential nutrients for plant growth.
  • Enhance Drainage: Add perlite or sand to improve soil aeration and water retention.
  • Adjust pH Levels: Test and adjust the pH, if necessary, to suit the specific needs of your plants.
  • Refresh with Vermiculite: Vermiculite can help maintain moisture and nutrients in the soil.
  • Regular Soil Replacement: For best results, replace or significantly refresh potting soil every couple of years to maintain soil fertility and structure.

It is a brilliant way to compost without attracting pests or making bad smells, and the worm tea and castings are fantastic enhancements for all types of soil. Explore our article, Does Potting Soil Go Bad? How To Tell if It’s Still Usable, to learn about the shelf life of potting soil and how to determine its usability.

Can Topsoil and Potting Soil Be Mixed?

A gardener holding freshly mixed garden soil in his hands.

Yes, you can mix topsoil and potting soil in large containers, especially if you’re on a budget. Make sure you sprinkle some excellent potting soil and nutrients around the base of your plant. I would go for worm castings, but you could also use a blood meal or bone meal. Be sparing on the amendments because over-fertilizing is absolutely a thing!

Best Soil for Outdoor Gardening?

The best soil for outdoor gardening is usually well-balanced loam soil. Loam soil is a mix of sand, silt, and clay in balanced proportions, providing an ideal environment for a wide range of plants. It offers excellent drainage, and good aeration, and retains moisture and nutrients effectively. Here are a few plants that thrive in loam soil:

  • Tomatoes: They require nutrient-rich, well-drained soil, making loam ideal for their growth.
  • Peppers: Like tomatoes, peppers do well in loam due to its balance of drainage and nutrient retention.
  • Carrots: Loam soil, particularly with a higher sand content, is perfect for growing straight, well-formed carrots.
  • Cucumbers: They need moist but well-drained soil, which loam provides, ensuring robust growth.
  • Zucchini: Thriving in moist, fertile soil, zucchini plants do well in loam soil, especially when it’s rich in organic matter.

If you’re growing tons of vegetables in containers, then you can always mix your potting soil with well-finished compost or topsoil. Just remember that at least 30% of the mixture is fresh potting soil for the best results. 

Wondersoil Organic Potting Mix

If I were buying online, I would personally go for the organic potting soil from Wondersoil because it contains worm castings and Mycorrhizae, which will help support healthy microbial life even in a container setting.

Best Soil for Container Gardening and Indoor Plant

For indoor plants or container gardening, the ideal choice is a high-quality, well-balanced indoor potting mix. This mix should be specifically designed for container plants, which makes it best to ensure optimal moisture retention, aeration, and fertility. Here are a few plants that thrive in such an environment:

  • Orchids: Require a potting mix with excellent drainage, often a specialized orchid mix.
  • African Violets: Best grown in a light, porous potting mix, ideally one tailored for African violets.
  • Succulents and Cacti: These plants need a fast-draining potting mix, often with added sand or perlite.
  • Herbs (like Basil and Mint): Prefer potting mixes that retain moisture but also drain well.
  • Ferns: Thrive in a moisture-retentive, rich potting mix with good drainage

Frequently Asked Questions (FAQ):

Which Soil Is The Best For Grass?

Loam soil is usually the best for grass because it balances sand, silt, and clay well. This balance ensures good drainage, nutrient retention, and aeration, all of which are essential for healthy grass growth. However, if loam soil isn’t available, sandy loam can also be a good choice, particularly for areas that require quicker drainage. Adding organic matter to other soil types can improve their suitability for grass as well.

Which Soil Is The Best For Starter Seed?

For starting seeds, a seed starting mix is the best choice. This specialized soil is fine-textured, sterile, and designed to provide the perfect balance of moisture retention, drainage, and aeration. It ensures optimal contact between seeds and soil, encourages healthy root development, and prevents the risk of disease, giving seeds the ideal environment to germinate and grow into strong seedlings.

What Are The Ingredients For Potting Mix? 

It’s not hard to make a potting mix for yourself, and you’ll save a ton of money.

You’ll also be sure you haven’t got any pests or pathogens in your soil, so you aren’t going to wake up to a cloud of gnats in your kitchen. You just need to buy some coconut coir, pumice, and worm castings. (You can also make your own worm castings and recycle food waste with a worm bin. I’m telling you, these guys are my best friends!) 

Is Organic Potting Soil Better? 

I prefer organic potting soil because gardening without chemical inputs is a personal goal.
It means that I know the food that ends up on my table won’t contain substances that could affect my health. For inedible plants, non-organic potting soil would be less of an issue. 

Can You Use Potting Soil in the Garden? 

Potting soil isn’t going to kill your garden plants, but it would be a waste of money. In a garden, you don’t need to focus as much on dense nutrition or drainage, as the natural environment supports plant growth.

Can Potting Soil Be Reused?

You can reuse potting soil, but I would sieve out any large roots first. You can then freshen it up with about 30% new potting soil.

To do this, tip your old potting soil into a larger bucket and mix it with the fresh soil. You can now use it for future pots.