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Buyer's Guide

How to Grow Cannabis in Soil

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If you decide to grow your cannabis in soil, choosing the right soil is crucial. Unfortunately, you cannot go and collect a bucket of soil from your garden, and start your growing process. 

That said, sourcing for the best soil to grow your cannabis in isn’t always a straightforward process. With so many things to consider such as cannabis-specific soils, pre-fertilised types, and bargain universal substrates, it could all get overwhelming especially for novices. And this is without considering the option of making your own soil from scratch! 

Though soil growing is probably the least demanding of any growing method (mostly if you grow in super soil), it is still one you need a proper understanding of to enable you get sterling results. 

Let’s talk about the best soil for growing cannabis.

Soil for Growing Marijuana

It goes without saying that a good soil is the foundation for a successful grow operation. If the soil you plant your cannabis in is bad, no other aspect will perform optimally. 

But, what crucial factors make up a good soil?

Besides adequate nutrients, the most important characteristics of good soil are:

  • Texture
  • Drainage
  • Water retention

In order for your marijuana to thrive, a balanced mix of oxygen and water need to be maintained throughout the life cycle of your plant. Overwatering your plant deprives it of oxygen, which soil that cannot hold water will lead to the plants drying out, thus injuring the roots. 

The Best potting soil for cannabis is one that has is both light in texture, and can hold an adequate amount of water – we will however get to that later.

A few options exist that can enhance the water retention, texture, and drainage of your soil. We will also look at these options later on in this article. 

What is Good Soil for Growing Weed?

In most cases, cannabis growers purchase commercial soil mixes that are pre-mixed, and specifically made for growing weed. Though dependent on some factors, these are usually done professionally and hence are usually fail-proof. 

Do you understand what goes into these mixes? What makes a good soil?

If you didn’t already know, we will tell you exactly what to look for in high-quality soil.

Generally, good marijuana soil should be dark and rich in appearance. It should also drain well, have a loose texture, and hold just enough water to prevent it from getting muddy. Soil that drains well does not pool water at the top for more than a few seconds nor does it take a long time draining at the bottom after a watering session. 

If you are not going the store bought way, a light composted soil that is rich is an example of good soil. If you run the soil through your fingers, it should lightly flow, giving you a great feel of the texture, and overall quality it has. With such a good base, you can make additions like perlite to improve its quality further.

In contrast, the appearance of bad soil could be clumpy, muddy, and waterlogged. Because it retains too much moisture, you could accidentally end up over watering your plants. You should also ensure that your soil is fully composted and does not have visible wood chips and other organic substances sticking out. Soil that is not well aerated will both hold too much water, and prevent access to enough air. 

As we mentioned earlier, do not use dirt for marijuana plants! What you collect from outside might be cheap, but you will end up with dismal results.

Best Soil for Marijuana Plants

Weed that is grown indoors, and that that is grown outdoors, has slightly different soil requirements. For indoor cannabis growing, a super soil, or a commercial soil that is specifically designed for cannabis plants is your best bet. Super soils win the overall game as they contain the right balance of phosphorus, nitrogen, and other beneficial nutrients already pre-mixed. 

If you are an outdoor grower on the other hand, you might have to make do with the soil in your garden, of course with a few tweaks here and there. In order to optimally use your soil, you need to understand its type, ie. Loamy, sandy, or clay and work it to the best advantage. Alternatively, you could dig a big hole and fill it with super soil or commercially bought cannabis soil. This will save you a lot of trouble and increase your chances of success. 

What’s The Best Soil for Growing Cannabis?

As we have discussed, not only is some soil unsuitable for growing cannabis, different types of cannabis may require different types of soil. When picking the optimal soil for your grow, you should consider the type of weed you’re growing, the climate you’re in as well as if you are growing indoors or outdoors. 

Let us look at the characteristics of a good soil in detail:

  • Texture

Ensure that the texture of your soil is light and loose. This kind of texture not only promotes root development, it also ensures that more oxygen gets to the roots. This ensures that the plant enjoys optimal growth, and health.  

  • Drainage 

A good soil for cannabis should have excellent drainage. After watering your plants, the water should not pool at the top or bottom, but should drain efficiently. Poor drainage leads to disease, poor yields, and even rot and plant death. 

  • Water retention

As important as drainage is, a soils’ ability to retain water is just as important. Proper water retention provides enough water for the plant and prevents it from drying out. Good cannabis soil will have an optimum balance between drainage, and water retention. 

  • pH value

The pH value of soil indicates how acidic or alkaline the soil is. The ideal Ph range for cannabis is a very slim margin of between 5.8 and 6.3. Incorrect pH could lead to decreased yields, and could even cause plant death. 

  • Nutrients

The best soil for marijuana contains nutrients in the required ratios. Fortunately, if you are purchasing commercially made soil intended for cannabis, this will already be taken care of. However, they might only last 3-4 weeks, and by the time your plants start to flower, you will most likely need to add more nutrients. 

An alternative to added nutrients is using organic substances like humus, guano, worm castings, and compost. The microorganisms in your soil will turn them into nutrients your plants will be able to access on demand.

Traits of the Best Soil to Use for Growing Weed

When considering the Soil to use for growing weed, If you’re using store-bought potting mixes, these are already optimally “tuned” for growing. Different story if you’re growing organically, though. Natural soil comes in four varieties: sandy, silty, loamy, and clay. But know that most soils consist of varying ratios of these soil types.

How to Improve Soil for Growing Pot

If you’re working with natural soil, chances are it won’t be perfect for growing cannabis—not from the start, at least. The texture may not be optimal or it may have poor drainage, for example. But you can improve any type of soil by adding amendments, most of which can be found in your local grow shop.

Coco coir: Lightens compact soil and provides increased water retention. 30% coco noir is usually ideal.

Perlite: Improves airiness and drainage of the soil, It also has remarkable water retention. Adding 10–15% perlite is usually ideal, though good-quality commercial soils usually have it pre-added.

Clay pebbles: Mostly used for hydroponic cannabis farming, clay pebbles could also be added to the bottom of your container or raised bed to prevent water from pooling at the bottom. They can also be put at the top to serve as mulch because they trap moisture, preventing excessive evaporation. They also cast a permanent shade on the soil which suppresses weeds, keeps the plant cool, and shelters beneficial microbes from the hot sun. 

Vermiculite: Like perlite, this is a heat-treated mineral which can be used to make soil lighter. It also retains water excellently. Unlike perlite though, vermiculite is used to increase the water retention in the soil. Both of them can be used at the same time, and 10% vermiculite is ideal.

Worm castings: Worm castings are a nutritional amendment as they contain a vast amount of useful organisms which benefit growth. This however is not all they do. They also improve drainage, texture, and the water retention of your soil. 20-25% worm castings added to your soil are ideal. 

Nutrients: Though having enough nutrients in your soil is vital, many growers usually make the mistake of making the soil “too hot”. This is because they end up adding manure, as well as vegetable scraps in a bid to “fertilize it”. Any vegetable scraps should be composted before they are added into the soil, and there is a thing like “too much” nutrients.  

Most times, increasing the nutrients in your soil is as easy as purchasing bottled solutions that are ideal for your plants’ phase of growth. 

Photoperiod vs autoflowering

Another factor to consider before you choose the perfect soil for your cannabis is whether you are growing photoperiod or autoflower strains. Autoflowers are generally more sensitive and a good choice for them would be a 50:50 mix of a light soil that is peat based, and coco noir that has added perlite for drainage..

If you are growing autoflowers, keep away from soils that are heavily fertilized soils especially with elements like bat guano. These will overload your plants with excess nutrients, and make the soil “too hot. The same applies to cannabis seedlings, which should also be grown with minimal nutrients. 

What Kind of Soil Should Cannabis Seeds be Grown In?

Plant your autoflower seeds in their final container as moving them later will cause them too much stress. Start by making a cup-sized hole at the center of the soil. You can then fill that hole with seedling/starter soil that has no nutrients, and finally place your seed there. This will ensure that your seedling can grow without being in contact with “hot soil”, which could burn it. 

For photoperiod plants, a small seedling cup/pot filled with starter soil that has no nutrients will do. You could then transplant them into bigger pots with grow soil in a few weeks when they are mature enough to tolerate the higher nutrient levels. 

No-till cultivation

“No-till cultivation” is a method of gardening which leaves the soil undisturbed for the duration of the grow. This means no stirring, digging, or overturning.  What this method does is that it allows the soil to create a thriving ecosystem which supplies the soil with helpful fungi, good bacteria, and other beneficial living organisms. No-till cultivation leads to greater organic matter retention, as well as increased water absorption as nutrients are constantly being “recycled” throughout the soil. 

Most Common Soil Mistake: Overwatering

The mistake that is most commonly made by beginners growing marijuana is watering their plants too often. Here, overwatering does not usually refer to giving your plant too much water. Usually, it refers to giving your plant water too frequently. This leads to a buildup of water which could cause the roots to rot and even lead to the plants’ eventual death.

How to properly water your cannabis grown in soil

  1. Before you add more water, wait until “the top of your soil” feels dry to your first knuckle (which is about 1 inch deep)
  2. If need be, add nutrients to the water you are using and ensure to adjust the Ph. Most growers neglect to adjust pH, this could lead to nutrient deficiencies as the plants are not able to properly utilize nutrients in the wrong pH.
  1. When watering your plant, pour water until you see at least 20% runoff drain out the bottom of your pot.
  2. Do not water your plant again until it meets the criteria described in point 1 above.

Conclusion

Not every soil is suitable for growing cannabis, and not all cannabis requires the same type of soil. Picking the optimal soil depends on the type of cannabis you’re growing, your climate, whether you’re growing it indoors or outdoors, and also whether you are growing autoflower or photoperiod strains. We hope we have given you enough information on how to grow cannabis in soil. After all, it is the very first medium that ever existed!

Lydia K. (Bsc. RN) is a cannabis writer, which, considering where you’re reading this, makes perfect sense. Currently, she is a regular writer for Mace Media. In the past, she has written for MyBud, RX Leaf & Dine Magazine (Canada), CBDShopy (UK) and Cannavalate & Pharmadiol (Australia). She is best known for writing epic news articles and medical pieces. Occasionally, she deviates from news and science and creates humorous articles. And boy doesn't she love that! She equally enjoys ice cream, as should all right-thinking people.