Growing Cannabis In Soil

When it comes to growing your own cannabis, there are a few key points you have to get right to achieve the best possible marijuana in the end. With this text, we aim to provide you with a detailed overview of what makes a cannabis-friendly soil and how you can recognise it.

Growing Cannabis In Soil


For growing cannabis, you can't just walk in the next flower shop you see and buy an ordinary potting mix for ornamental plants and flowers. It’s not that simple! Of course, cannabis plants will grow in this kind of soil, but they will not reach their maximum potential. Cannabis requires a specific composition of soil to grow ideally.

With this text, we aim to provide you with a detailed overview of what makes a cannabis-friendly soil and how you can recognise it. We’ll also share tips on how to make the perfect organic super soil.

Let's get started!


Important Soil Factors

A good soil is the foundation of a successful grow operation. If the soil is bad, every other important aspect of your grow can't perform to its full potential. But what are the crucial factors that comprise a good soil?

The most significant characteristics of soil (besides the included nutrients) are its texture, drainage, and water retention. A balanced mix of water and oxygen is required at the roots throughout the life cycle in order for your cannabis to thrive. If the soil is overwatered, then there is not enough oxygen present. On the other hand, if the soil can't hold the water, the roots can be injured by drying out.

The best soil is one that has a light texture and can hold just enough water - but more on that later.

There are a few options that can enhance the texture, drainage, and water retention of your soil. The most common is to add perlite to your grow mix (if it hasn't some in it already). These are very light, airy, white "rocks" that add oxygen to the mix. They also increase the overall drainage ability of your soil.

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Vermiculite is another option that "lightens up" heavy soils and improves water retention. Coco coir is made from coconut husks and also improves water retention, but doesn't make the soil too heavy. This way, the roots develop much faster and the plants are less likely to suffer from overwatering. Cannabis plants seem to love worm castings; yes, that’s basically worm poop! They improve the texture, drainage, and moisture retention of your soil. Plus, they normally contain high levels of beneficial microorganisms, which is an advantage over the other options here.


How To Recognise Good (And Bad) Soil

Most growers tend to buy commercial soil mixes that are made for growing cannabis. Usually, these are already effective soil mixes. But for those who aren't quite sure, here is what to look for from high-quality soil.

Generally speaking, good soil should appear dark and rich, have a loose texture, drain well, and hold water without getting too muddy. Draining well means that the water doesn’t pool on top of the soil for more than a few seconds, and doesn't take forever to drain out the bottom when you water.

An example of a good soil for cannabis is a rich and light composted soil. Good advice is to run the soil through your fingers. By doing so, you get a great feel for its texture and overall quality. A light yet rich soil is nice to start with. You can then add perlite or any of the aforementioned options to your liking. It depends on how well-drained your soil should be. When you want to use a lot of supplemental nutrients, for example, you should use more perlite. The opposite is true if you don’t plan on adding many supplements. If you don't want to use any nutrients at all, you can make your own super soil (again, more on that later).

In contrast, bad soil can be recognised as being muddy, clumpy, and waterlogged. It retains too much moisture, putting you at greater risk of accidental overwatering. Moreover, there shouldn't be too many visible wood chips in the soil. Wood chips signal that your soil is not fully composted yet, meaning all the goodness in the wood is not available to your cannabis ladies. If the soil looks like one solid object, it will hold too much water and not enough air.

Although we hope no one ever does this, we have to mention it just in case: Don't use dirt soil from outside! We know you sometimes want to keep things cheap, but it just doesn't work like that.


Best Soil For Indoor And Outdoor Cannabis

Whether you grow your weed indoors or out, the soil has to meet slightly different requirements.

The best soil for indoor cannabis is either commercial soil specifically designed for growing cannabis plants, or a super soil. You have several high-quality commercial options out there to choose from. They should be organic and not contain any time-released chemicals. Super soils could be considered the best solution for your indoor cannabis because it offers the right balance of carbon, nitrogen, phosphorous, and a wide range of other beneficial nutrients.

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If you grow outdoors in a garden, you normally have to use soil that already exists in nature. The three main types of this are sandy, loamy, and clay soils. Most of the time, soil is a mix of these three in different ratios. Depending on the ratios, you get varying degrees of quality. When growing outdoors is your only option, it is advisable to dig a big enough hole and use the organic super soil we are going to tell you about below. Alternatively, you can use pots with plants grown outside. With this option, everything we said above regarding indoor soil applies.


What Is Organic Super Soil?

It has been mentioned several times throughout this text and now we are going to tell you exactly what it is. The key factor here is life. A proper super soil is full of life. To give you an idea of what that actually means, a shot glass filled with organic soil contains more individual living organisms than humans on Earth. That's mind-blowing, isn't it?

Biodiversity is the keyword when it comes to a proper organic super soil. The life in the soil thrives on diversity. Each organism serves its purpose in the web of life. This web is not only self-sustaining but capable of converting and providing readily-available nutrients to your plants. To grow using organic super soil may require nothing more than adding water when needed. That's it!

But which components comprise the perfect super soil?


How To Make Your Own Organic Super Soil

First of all, making your own organic super soil is a bit of a trial and error process. If you've got your basic mix down, it may require some minor adjustments over several seasons.

To start, you can either use a commercial soil product as a basis to build upon, or you can make your super soil from scratch. For this article, we choose to make it from scratch.

You begin with your base mix. For that, you must combine compost, organic material (like peat moss or coco coir), and aeration (perlite or vermiculite) in equal parts. This base mix will account for approximately 20% of the total volume of your final soil mix. A good rule of thumb for this recipe is: 1 part compost, 1 part organic material, and 1 part aeration agent.

Next, you will have to establish a fungal population. A diverse microbiology in your soil will do just that. Fungi develop mycorrhizal relationships with the rhizosphere (the root system of your plants). It's basically a symbiotic friendship where both the fungi and your cannabis plants benefit. Some great amendments for building fungal life are kelp meal (30g per 19l), humic acid (30g per 19l), and mycorrhizal inoculant/endomycorrhizae powder (¼-½ teaspoon per 3.8l).

Then you must establish a bacterial population. This is equally important as a fungal population and helps to break down sugars and convert them into readily-available macro and micronutrients. It will further establish and maintain the immune system of your plants in order for them to be more resilient against pests, disease, and adverse environmental conditions. Ingredients that provide beneficial bacteria include vermiculite (up to 20% of the total substrate) and bat guano (up to 5% of the total substrate).

The last step is to fortify your organic super soil mix with sources of macro and micronutrients. Usually, these nutrients are provided via bottled fertilisers. With organic super soil, you amend them in the base mix instead so they can be released and/or broken down as food for your plants. There are several amendments that you can use to fortify your soil mix. Here are some examples of the main nutrients or benefits they provide:

  • Blood meal (nitrogen)
  • Bone meal (nitrogen, calcium)
  • Rock phosphate (phosphorous)
  • Epsom salts (magnesium)
  • Crustacean meal (nitrogen, phosphorous, calcium, magnesium)
  • Dolomite lime (pH balance, magnesium)
  • Azomite (micronutrients)
  • Wood ash/bio char (potassium)

If you have followed these steps, you will now have mixed together a terrific organic super soil that every grower can be proud of. Use this as the foundation for your grow operation and you will notice how well your cannabis plants grow and how amazingly they thrive. Now, you just have to get the other growth factors right. The good news is, with your organic super soil, you don't have to worry about feeding your plants correctly anymore; you just have to give them water! This frees up your mind for all the other stuff a grower has to think about to be successful.

Miguel Antonio Ordoñez
Miguel Antonio Ordoñez
With an AB Mass Media and Communications degree, Miguel Ordoñez is a veteran writer of 13 years and counting and has been covering cannabis-related content since 2017. Continuous, meticulous research along with personal experience has helped him build a deep well of knowledge on the subject.