Cannabis Growing Guide: Soil

Cannabis Soul Guide

For those of us who grow indoors or in pots, it can be a bit tricky to choose the best soil. This is especially hard for new growers who are plied with so much false advertising. We need to make sure that the soil we choose has plenty of nutrients and will support our plants right up until they are ready for harvest. There are quite a few different choices available, so today we are going to sort through the most popular and talk about their pros and cons as well as the type of grower they suit best.

First, let’s have a quite look at soil growing itself and what it has to offer growers. For some growers, a hydroponic system is just easier, but for others, soil is the only way to go.


  • Soil is significantly less expensive than a hydroponic system, as well as being far less complicated.
  • First-time growers should definitely grow with soil as the plants are more likely to thrive with minimum help.
  • Fertilisation and irrigation are much easier in soil than in hydroponics.
  • Soil growing has been around for far longer, meaning we know a lot more about it and there is far more information available.


  • Soil usually takes up more space and can be messy to deal with.
  • Insects and other pests are far more likely to settle down in soil and nibble on the plants.

Soil Structure

Unfortunately, it isn’t as simple as going out and just buying some soil. First, we have to consider the different types of soil available and choose which one will be best for our plants.

Clay Soil:

Thought to be the best organic option for cannabis growing, clay is bursting with minerals and nutrients. This means it creates crystalline particles and is extremely easy to shape, it is also less messy. However, because of its particular structure, it doesn’t drain particularly well. The overall effort with clay soil is intense, and many believe the results aren’t worth it.

Silt Soil:

Silt soils hold moisture well and contain a lot of minerals, including quartz. Despite it being great at containing moisture it also drains very well and is easy to work with. Silt is perfect for seedlings as it is soft, malleable and very fertile. It gives them a lot to work with and feeds them extremely well. Silt is probably the best for anyone who is hoping for a larger yield.

Sandy Soil:

Sandy soil drains well and is easy to prepare for the plants, it is also extremely easy to aerate. This means it gives plants plenty of breathing space which makes it great for indoor growing.

As one might expect sandy soil can get dry quite quickly and struggles to absorb moisture after watering. It also tends to lose nutrients rabidly and may not be able to give young plants everything they need.

Loam Soil:

So this soil is a bit of an all in one, a mix of the three above soils. This soil can be extremely easy to work with if prepared well and will usually have an organic component. The PH is pretty much neutral which is ideal for most growers, a sort of blank canvas. It drains well, is fertile, holds nutrients and breathes. The primary downside with this type of soil is the price, it is usually pretty expensive.

Choosing The Right Soil

Selecting the perfect soil depends on a number of factors like grow space and type of strain. There is no guarantee for the soil so it’s a good idea to buy what we think will work well and see how our plants go. It’s definitely a learning process, finding the perfect strain.


Ideally, we want our soil to be very slightly acidic rather than alkaline. A PH of 5.8 – 6.3 is around ideal and it is possible to test the soil before using it.


The soil should come with a good array of nutrients already, often it will say on the soil. We shouldn’t try to directly fertilise plants, but should only use broken down organic matter. We can also add nutrient-rich potting soil mix to ensure the plants are getting everything they need. There will be different nutrient needs for different stages of growth.

It can be argued that the most important aspects of soil are the drainage, the water retention and the texture.

What we are looking for in quality soil:

  • Water retention that holds well without causing the soil to become mud.
  • A loose texture, if the soil is too tight and packed it won’t breathe well.
  • A rich and dark colour, if it is light brown and dry it is likely lacking in nutrients.
  • Good drainage, basically meaning water shouldn’t pool on the surface of the soil for long, it should sink through.

There are a lot of ways that we can help soil along if it can’t be found in this perfect state.

In order to improve the drainage and the oxygenation of the soil, we can add perlite. This is a mix of airy rocks that break up the texture of the soil a little.

If we want to improve the water retention of the soil to ensure the roots have enough to eat, we can add vermiculite. This works well mixed with perlite to ensure we don’t over drain. It helps the soil to absorb a little more of the water.

Finally, if we need to improve the water retention without increasing the density of the soil we can use coco coir. This is all-natural and made from coconut husks and will help the roots to develop quickly ensuring the plants are well fed.

Hopefully, this will help inexperienced growers know what to look for when buying potting soil for their new babies. There are many places online that we can buy soil specifically for cannabis growing, but if all we have is a garden centre we know how to choose the best quality soil possible.

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