Do I need to use potting soil in my pots?

When I first started growing plants in pots I wondered if I really needed to buy “potting soil” (called “potting compost” in the UK), or if I could use something cheaper, like topsoil or regular garden soil.

I read a few articles that said you really should use it, but aside from potting soil being lighter, and therefore the pots easier to move around/less likely to collapse a balcony, I wasn’t really sure what the benefit was.

I did see that potting soil was a lot more expensive than topsoil, which was often on special for $1 a bag. And I suspected that special “potting mix” might be just another unnecessary upgrade designed to part a newbie gardener from the cash in her wallet.


Then I started taking night courses in horticultural science at a local college and learned, to my surprise, that there are actually good science-based reasons to use potting soil in your pots! I still remember the night in class when we covered this material and I finally understood (yes, this was such a momentous occasion that I vividly remember it more than a decade later—some things are just important 😉 ). So if you want to know the science (well, a simplified version of it) keep reading as I love sharing this.

If you just clicked on this article to find out whether you really had to use potting soil for container gardening—the answer is yes—you can head off to the store now while the rest of us talk soil.



The functions of soil

As far as plants are concerned, the soil they grow in needs to fulfill four functions:

  1. Anchor roots
  2. Supply water
  3. Supply oxygen
  4. Supply nutrients


Because a pot is a completely contained environment, unlike a farmer’s field, the small amount of soil in the pot has to meet all four of these requirements. In a farmer’s field the plant’s roots can spread to get water or get away from too much water, seek out nutrients and oxygen, and anchor themselves sufficiently. In a pot, they’re limited to just the soil you provide. That soil has to hold some water, but not too much, and provide space for air, water and roots to permeate it. It also has to contain nutrients to feed the plant.


Water is the key

In the great garden soil vs. potting soil debate there are two main factors to consider, and they both relate to water:

  1. Regular garden soil is usually too dense (i.e. too tightly packed together, because it’s made up of a lot of small clay and silt particles) to allow water to drain well within the confines of a container. There’s just not enough room from the top of the pot to the bottom of it for this process to take place.
  2. The water table (i.e. the point at which soil is saturated with water) in a pot is essentially at the bottom of the pot. In a farmer’s field it’s usually several feet or more deep in the ground (this is the super-abbreviated explanation, but in a field there are different layers of soil, with different textures, and the water table is way down deep). Because of this, the soil at the bottom of a pot can easily become, and stay, saturated if you fill the pot with regular (i.e. dense) garden soil.

Most plants can’t grow if their roots are constantly sitting in water. Therefore, because the soil in a pot is not nearly as deep as a farm field or garden, you need a looser, better draining soil mixture in a pot than in a garden so that the roots have room to grow in soil that’s still adequately moist, but is above the water table.

That’s why you need to use potting soil in a pot.



Oxygen and nutrients are also factors

Supporting reasons include that garden soil is likely to be too dense (i.e. the particles too fine and stuck together) to allow oxygen to get to plant roots. It also may or may not have enough nutrients (especially if it’s very sandy soil or is from an area with nutrient depleted soil), although you can certainly always add fertilizer to a pot later.


Potting soil provides the right structure and nutrients for plants to grow—ideal mixes are usually made up of about 50% solid materials (45% mineral particles like sand, silt and clay and 5% organic matter/compost), 25% water and 25% air (oxygen).


So that’s why you should use potting soil in pots. Potting soil allows your potted plants to access the right amount of moisture, oxygen, nutrients and moisture, while providing a structure in which to anchor their roots.


Woohoo! If you’re as excited about that explanation as I am we should go for coffee, or go shopping for potting soil together—I think we could be friends! Seriously, it’s important stuff.

But I get it if you don’t really want to know all that. I’m here to help you know what to buy so that you can grow nice plants and have a fabulous garden. I appreciate your patience.


A couple other questions I often hear about potting soil are:


Is there a difference between brands/types of potting soil?

Yes. There are different formulations for specific needs—e.g. general container gardening vs. for particular plants like cacti and succulents. For general outdoor use you just want to look for a label that says potting soil or container gardening mix. Some brands have fertilizer added and/or a product that helps retain moisture—I often buy this kind as our summers can be very dry and I can use all the help I can get.

Note that you do get what you pay for in most cases. I’ve had friends buy “potting soil” at the dollar store and, well, it wasn’t as advertised. You don’t have to buy the most expensive kind around, but just make sure it’s of decent quality. If it costs $1 it’s likely not what you’re looking for.


Can you make your own potting soil mix?

Absolutely. If you need a large quantity of potting soil or have concerns about buying bagged soil you can alter garden soil to make its texture coarser and improve its structure. There are plenty of DIY potting soil recipes on the internet, This one looks pretty good.


I hope you found this article helpful. If you did, please leave a comment below or share this article, and your new knowledge, with your friends.







  1. Elaine Petermann on March 8, 2017 at 8:46 am

    My husband is the scientist in the family who grows lettuce and herbs under lights starting in December so we’ve had fresh lettuce in February. This explanation was concise and helpful for the me — the slap-happy gardener in the family.

    • Jennifer on March 9, 2017 at 8:01 pm

      Fresh lettuce and herbs in February! That’s awesome! Glad the potting soil explanation was helpful.

  2. Angela Vellekoop on March 8, 2017 at 5:27 pm

    Fascinating and entertaining – I will definitely buy good potting soil from now on!

    • Jennifer on March 9, 2017 at 8:02 pm

      Excellent! Thanks Angela.

  3. Garth Wunsch on March 9, 2017 at 10:39 pm

    ‘ the rest of us can talk soil” Is that like talking dirt(y)? Great explanation.

  4. Iris Powers on June 14, 2019 at 5:15 pm

    I am a biologist who enjoys an explanation. Thank you.

    • Jennifer on June 27, 2019 at 9:30 pm

      You’re welcome, Iris. Glad to be able to share what I’ve learned.

  5. Russell on April 13, 2020 at 9:23 am

    Thanks, this was very useful. Even years after you wrote it.

    I was trying to find out if I could just use compost, or if I also need to use topsoil.
    And now I might start looking specifically at potting soil.

    In the meantime, I think if I do something like 75% compost, and 25% topsoil, then that sounds like it could be okay right? I have a HUGE bag of compost, but only a small bag of topsoil.

    I remember compost dries out quite quickly, so I thought the above ratio might help.

    For context: I have a yard with no ground soil, so everything is in pots or containers, or hanging baskets. UK North east climate, warm and humid, but the yard does not get much sun.

    • Jennifer on April 20, 2020 at 6:05 pm

      Thank you for letting me know this article was helpful, Russell. Soil is timeless, thankfully! A combination of compost and topsoil could work, depending on what kind of plants you want to grow–you might want to add some horticultural grit or sand to help loosen it up. There are lots of potting soil recipes online with proportions included: I like this one from Fine Gardening magazine as it gives you a basic recipe and then suggests modifications depending on the types of plants you intend to grow in it:

  6. Holly Renegar on May 3, 2020 at 7:09 pm

    Thank you so much. You explanation was to the point, easy to understand and very helpful! Let me know if you ever come to Boulder, CO and I’ll take you out for coffee or, better yet, have you to my house for coffee and sit in my back yard and enjoy the flowers, etc! We sure could be friends : )

    • Jennifer on May 4, 2020 at 6:05 pm

      Thanks Holly! Would love to take you up on the offer, but no plans for travel for now. Hope you take the time to sit and enjoy your flowers!

  7. Kristen on June 12, 2020 at 5:49 pm

    Thanks for advice!

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