Air Pruning Cannabis Roots: Ways To Increase Yields

Pruning is one of the most popular plant training techniques, where you essentially snip away unnecessary parts of the plant to enhance aeration and light penetration in the canopy. But this pruning happens only above the soil, what about what’s under the soil, i.e., the roots? 

That’s where air pruning comes into play. But unlike regular pruning training methods, you don’t need any scissors or blades for this. You’re not cutting any of the roots. Instead, you create an environment where the roots “prune” themselves. 

Doesn’t make much sense, right? Wait till you learn more about this awesome evolutionary trait that your cannabis plant can benefit from. Here’s everything you need to know about air pruning cannabis roots with the help of the right containers and conditions. 

What Exactly is Air Pruning?

Before we get into the nitty-gritty, let’s refresh our minds on what exactly is air pruning. It is a natural process that occurs in the root zone of your cannabis plants. Essentially, when your cannabis plant is growing, the roots expand within the soil looking for more nutrients. Once the roots get exposed to outside air, especially dry air, they stop developing in that direction. 

This is a natural process that evolved in plants and is completely logical. The plant’s roots need to grow to find nutrients, but there are no minerals in the air. Since the roots don’t need to grow in the air, the plant actively stops the roots once they reach the air. Instead, the roots are redirected in another direction; the fibers of the roots start growing laterally to stay within the soil. 

As mentioned already, this process is natural, but growers have learned to harness it to improve their plant’s health and yield. This came to pass, thanks to many growers finding their plants root-bound, meaning the root ball grows so much within the soil that it runs out of space, leading to symptoms like slow growth, nutrient deficiency, and mold. 

To counter this problem, growers started experimenting with different types of containers, including burlap bags to fabric pots. What they found was that fabric or smart pots, as opposed to plastic pots, prevented root-bound plants to a great extent by allowing the roots to get exposed to air so they stop growing when it’s time. 

As a result, growers no longer have to worry about their plants getting root-bound, suffering from growth or mold problems, and sometimes, even about low yields. Many experts claim that air pruning can even improve the yield to a certain extent. 

Why is Air Pruning Important?

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Let’s understand the process in detail. Your cannabis plant, like all plants, needs a lot of carbon dioxide from the air, which is absorbed via stomata, i.e., small structures that act as valves on the plant’s stems and leaves. Plants also require oxygen to grow well, and this gas is absorbed in the rhizosphere via the roots. To get more details on this, check out this post from the University of Washington. 

The roots absorb oxygen via the tiny pockets of air in the soil, which is then used to make nutrients. These pockets in the soil also contain moisture that makes the air in the rhizosphere humid, which is what the plant’s roots are like. On the other hand, the air on the outside, even in a tropical climate, is too dry for the roots. 

To understand the process better, you need to understand the root’s anatomy. When plants germinate, they grow a single seminal root, and as the plant grows, they develop secondary roots. In some plants, the seminal root turns into a tap root, and in other plants, the seminal root grows several secondary roots that grow out. 

Over time, the root network expands and gets established into the soil. This healthy root network should be white and ideally have an earthy scent — important to note as you learn more about root pruning and moldy roots. 

These roots absorb water and nutrients from the soil, and despite doing so throughout their length, the most amount of nutrients are absorbed via the tip of the roots. The tip has also evolved with a protective cap that protects the roots from damage as they push past the soil while developing. Behind the root tip is where absorption happens, especially via tiny hair-like structures that absorb water. 

In an outdoor, natural ground, the roots of plants grow in all directions and they also branch freely to look for nutrients and water. Since the ground is usually free of any blockades, except a rock or two somewhere, the roots can grow big and support the plant in growing. And those roots that grow toward the surface are automatically pruned by air and redirected into the soil. 

Root Bound Cannabis 

The problem occurs in a container, where the roots have limited space to grow. Roots are ever-growing in search of food and water, which is crucial for your plant’s health and growth. However, in a container or a pot, the roots may quickly run out of space. 

Eventually, the roots will bump into the bottom and sides of the conventional container, whether it is made of plastic or ceramic. But since the root does not know what’s happening — not like it has eyes — it will keep pushing toward the walls and eventually start wrapping itself around the insides of the container.

The roots never get the signal that it’s time to stop growing, and so they keep expanding until they have run out of space within the container. Congratulations, your cannabis plant is root-bound.

And a root-bound cannabis plant is something you never want. While the roots are big, they are so big there’s barely space left for air, nutrients, and water. This can lead to all kinds of problems for the plant, and over time, it can experience nutrient deficiency, drought, suffocation, and even slimy roots. 

In some cases, the roots may even twist and strangle themselves, which is highly stressful for the plant since roots are quite sensitive. This can further affect the plant’s health and growth. 

When you remove your cannabis plant from the container, it will be very evident if it is root-bound — the soil and the roots will come out as a single mass and most of it will be roots with little soil, looking something like spaghetti. The roots will also have no fibrous growth near the tip, and the way to fix this is to transplant the cannabis into a bigger container and sometimes even prune the roots. 

Generally, you can simply untangle the roots if they’re still white, but sometimes, you may need to snip some tips to free the roots. Some growers even recommend making vertical slits in the root mass to improve aeration within but remember that this is quite stressful for the plant and should be the last resort. 

This is where air pruning comes into play. Air pruning prevents the roots from getting bound up inside the container, so you don’t have to worry about it. At the same time, it encourages the development of a dense root ball, thanks to better oxygenation of the medium. This can further improve your plant’s yields. 

Essentially, air pruning allows you to make the best of your growing medium, and it is especially crucial when you are using pre-fertilized substrates or super soil. Air pruning also allows better access to nutrients, leading to a root mass that is more like a spider web and less like spaghetti. 

How to Air Prune Cannabis?

As mentioned above, air pruning involves exposing the roots to air, but that doesn’t mean you start pulling the roots out of the soil or cutting them. On the contrary, air pruning is a rather passive process that happens on its own — you just have to provide your plant with the necessary conditions for the same. 

And you can do that by making air available to the roots with the help of specialized containers that encourage air pruning. So, as long as you grow cannabis plants in a right-sized air-pruning-supportive container, the process will occur on its own without any input from you. 

But what are these containers? They are a significant upgrade from regular containers and an investment in the true sense. The trend began with growers using burlap bags but the community has come a long way and there are a few innovative and better options available for you. 

But each of these containers has one thing in common — they contain holes or slots on the walls that allow the roots to get exposed to dry air, which stops them from growing further. There are dozens of such container types available in the market, but let’s take a look at the most common ones that work best for cannabis plants. 

1. Smart or Fabric Pots

Fabric pots have many names — grow bags, smart pots, grow pots — but they are the same, usually made of fabrics. The fabric used for smart pots is breathable and sturdy enough to hold the weight of the plant while allowing the water to drain well. For the same benefits, fabric pots are incredible containers for fine soils or if you’re growing in a humid environment. 

If you’re growing a massive plant with a lot of soil, you can still use fabric pots. Some models come with support rings or ribs that give them a semi-rigid structure, which is perfect for bigger plants that need additional support to stay upright. 

So, what’s so smart about fabric pots? Nothing much. Fabric pots are as analog as terracotta pots, but they are called smart pots because they encourage air pruning. The tiny pores in the fabric allow the roots to get exposed and air pruned, unlike conventional pots that lack any holes for air pruning. 

2. Plastic Air Root Pruning Pots

On the other hand are air pruning containers that are made of plastic but covered in holes all around. These holes vary from an inch to a few, depending on the size and style of the container, but high-quality ones don’t just contain random holes placed everywhere. Good quality containers have holes spaced out in a minimum ratio of 10:1 to the material, which is the ideal ratio according to a study conducted by the University of Florida. 

There are many types of air pruning pots available in the market, ranging from thin ones that are suited for smaller plants to thick and sturdy ones that can support a super cannabis plant. You need to pick one as per your cannabis strain’s size and growth pattern. 

Another thing to keep in mind when choosing air pruning pots is the style. If you’re using soil that’s rich in clay, loam, or peat, you should use a pot with larger holes since the growing medium is more susceptible to clumping together. On the other hand, loose or sandy soil requires smaller holes. 

If you want to save some money here, you can even make your own air-pruning pot at home. All you need to do is cut out some holes in a plastic container and your air pot is ready. However, we don’t recommend this approach — they generally suck. It’s better to just spend some money and get air pots. 

3. Air Pruning Pots: Indoor vs Outdoor

One of the confusions you might face when using air pots is which one to use depending on your plant’s location — outdoor or indoor. So, if you are growing your cannabis plant indoors, you can use whatever you like with any medium of your choice. Generally, indoor growers prefer using fabric pots with coco and soil mediums, and you can even use black fabric pots that usually get sold at a discount. 

Smart containers have another benefit for indoor growers — they are lightweight and easy to move around, so if you ever need to make any changes to your indoor setup, a fabric pot will be a lot easier on your back. 

On the other hand, if you are growing cannabis outdoors, you should consider using geotextile pots. They are cheap and effective. However, you still need to keep an eye on the roots as they can sometimes dry out too quickly in geotextile pots. 

Air pots are generally recommended for massive cannabis plants that won’t be moved around a lot during growth. They tend to be heavy and lack handles, so moving them around is a challenge that most of us would rather avoid. 

How to Know If Air Pruning Is Successful?

Air pruning is a passive process, so checking it is a little tricky. As with most things, you can’t just whip out the roots and inspect them; you need to be patient and use the correct approach if you want to know whether your plant’s roots are being air-pruned or not. 

The best and safest option is to wait until harvest; you can check the condition of the roots after harvesting the buds. But if you don’t want to wait until the end of the line, keep an eye on the holes in the pot you are using. 

If you notice any white root tips growing out of the holes, it’s time to take matters into your own hands. Remember, air pruning occurs when the roots are exposed to dry air; if they keep growing out of the hole, it’s a sign that they are not getting enough air in the soil or the soil is too moist. 

If that’s the case, consider placing your cannabis plant on a bench, moving it to a location that has better ventilation and airflow, or adding a fan to the setup to improve aeration within the growing medium. And henceforth, you can consider adding a more airy growing medium to the soil. 

Other Factors Concerning Air Pruning 

That’s all the basics of air pruning covered above, but there are a few things you must keep in mind that may come in handy either now or in the future. Let’s take a look at these few things. 

1. Air Pruning Mother Plants

Sustaining a mother plant is exciting yet arduous — it’s probably your favorite and most cared-for plant because it gives you more plants, and you can use a smart pot to sustain your mother plant. This is because it is not recommended to keep a mother plant in a small pot for a long time, and non-porous containers are usually not good for mother plants even if they are the right size. 

So, if you want to avoid problems, especially root binding, with your mother plant, it is a good idea to use smart pots. And if your mother plant is already root-bound, consider removing two-thirds of the root network and placing it in a larger container. It’s risky, but it’s worth it considering it’s your mother plant — just remember to give it enough time to recover before taking out clone cuttings from it. 

2. Pruning Roots Manually 

Many growers recommended pruning the roots manually to ensure better growth of the root network. If you want to take this approach with your root-bound cannabis, cut the base into four parts and break apart the roots. Remember to disrupt the spiral shape so the roots can grow outward, not around themselves. 

It is never recommended that you prune the roots manually if your plant is growing well and not experiencing root binding. Roots are sensitive and pruning the roots manually will shock the cannabis plant. 

3. Use Rhizosphere Bacteria for Better Root Development 

Whether your plant is recovering from root binding or you just want to improve your plant’s health further, you should consider using rhizosphere bacteria with air pruning. This bacteria acts as a biofertilizer that fixes plant nutrients, produces growth hormones that stimulate plant growth, protects the roots from other pathogens, and much more.

You can find rhizobacteria in any horticultural store, but be sure to use one that is suited to your plant and ambient environment. Always follow the manufacturer’s recommendation on using it to ensure optimal results. 

4. The Four Inch Rule 

If you want to grow a massive cannabis plant and want bigger yields, try the four-inch rule. Essentially, this rule requires you to start your cannabis plant in a 4 inch rockwool cube or fabric pot. Doing so will encourage maximum root development in the first four inches, and since these roots will be air-pruned and well-established, they will develop bigger once transplanted into the final container. The result would be a massive cannabis plant with significantly higher yields. 

Summary: Air Pruning Cannabis Roots: Everything You Need to Know 

In conclusion, the art of air pruning can be a game-changer for your cannabis cultivation. Air pruning addresses the roots and how they navigate within the soil. When all is good and jolly, air pruning improves root health and encourages better plant growth. And when all’s not well — root binding — air pruning allows you to prevent this problem by ensuring the roots don’t get too dense for their own good. 

By allowing roots exposure to dry air, these containers trigger a passive yet transformative self-pruning mechanism, maintaining a robust and well-aerated root system. The benefits are manifold – from averting nutrient deficiencies to enhancing oxygen absorption and moisture balance. 

Whether indoors or outdoors, choosing the right container becomes pivotal, and monitoring the success of air pruning involves keeping a keen eye on root tips peeking through potholes. Ultimately, integrating air pruning into your cannabis cultivation not only safeguards against common pitfalls but also propels your plants toward a flourishing and productive future.

And this is one of the many ways you can support and protect your cannabis plant. To know more about such nifty methods of improving your cannabis cultivation, stay tuned to our blog. We post regular guides that will make you a better grower than ever before.