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The roots of a cannabis plant are the main reason why growers experience huge yields, small yields or suffer from problems with nutrient buildup. It is common practice for many growers to plant their seed or clone and allow the roots to become root bound. The grower will check for roots growing out the bottom of the pot and transplant the cannabis plant to a larger pot once they do.

How Does Air Pruning Work?

When a shoot of a cannabis plant is pinched out, two new shoots form and grow in the place of the old one. Many growers really take advantage of this and top their plants to grow as many new shoots as possible. During this time however, the root base is neglected to some degree and is not given the chance to prune itself naturally.

poor developing cannabis plant roots

There are many ways to develop roots poorly. Air pruning can help tremendously to make sure your cannabis plant grows a well developed root system.

Air pruning occurs when roots are exposed to air, once the tip comes into contact with air it will react by pruning itself and create a double tip. Once the tips have grown back they will make their way through the medium again, where they will eventually come into contact with the edge of the pot again. Effectively you are constantly pruning the roots and once they start pruning the root mass will increase by almost 500%. The tap root is not as in control as when growing with normal pots and as a result the roots choose to grow out laterally and continue this until they have been pruned many times over. The result is a round root ball that looks the same all over, showing you you’re on the right track.

What Pots Are Best?

You should create an environment where the roots growing into the medium have a chance to be exposed to air so their tips dry out. The best pots to incorporate air pruning into growing cannabis are fabric felt pots, these are easy to make and very rewarding. Another way to promote air pruning is to take your old plastic pots and create pencil sized holes all the way throughout. Alternately you can cut vertical slits in your pots to create a continuous air flow. When using air pruning pots like this you will notice how the roots can be seen growing out through the holes and back in sideways rather than going around in a circle. The idea is to create a root zone that is far more compact than that of a cannabis plant grown in a regular pot. This will allow the plant to have more roots without becoming root bound.

This 5 minute instruction video shows the easiest way to make your own air-pruning fabric pots. All you need is the right fabric, preferably felt, and a sewing machine.

Will It Increase My Yields?

Yes! Air pruning is the way to get huge yields from your cannabis plant as you’re creating a monster sized stem and a very strong root system. This is true for both indoor and outdoor marijuana growing. The plant will grow much more vigorously and will grow thick hard woody stems and one final fat trunk. Your plant will grow much better and will be able to absorb more nutrients, this also means you can feed at a higher E.C. than without air pruning. Comparing the root zones of air pruned and non-air pruned plants, the results can be very clear. Without air pruning most of the roots are usually running circles against the outside of the pot, while air pruned roots are dense throughout the entire pot.

strong cannabis plant roots

Air pruning can help your cannabis plant develop a strong, healthy root system and a giant tree trunk-like stem.

What About Transplanting?

When you transplant an air pruned cannabis plant, you have the opportunity to really advance the layout of the roots and develop even heavier root pruning. One technique involves breaking apart the base and side of the root ball and lay it out into the new pot. By doing this you change the dynamics of the root zone and force it to grow throughout the medium. Another good technique is tearing the corners of your root ball open and planting the torn root ball half way into your new medium. This way the cannabis plant has a chance to develop an even denser root ball as opposed to the roots growing down and in a spiral shape like when growing cannabis without air pruning.

breaking the root ball

By breaking up the root ball you can stimulate extra root growth and is definitely a good idea when transplanting.

Can I Prune Roots Myself?

Cutting the root ball with scissors is a great technique to ensure better root development. Many growers cut the base of the roots in root bound pots into 4 and break up the spiral shape. Now the plants roots will grow away from the spiral shape and it technically has four new root zones. Another good idea is to chop down the sides of your pots and cut away the roots growing around the sides. The aim of this technique is also to stop the constant spiral shape, even though it sounds like you’re cutting your plants up.

A third effective technique to increase the root mass of your cannabis plant that does not take much time involves pulling out roots as they appear at the base of the pot using tweezers. Not only will this prune the root but it will create a knotted ball of roots at the bottom of the pot. By constantly doing this your bottom root zone can be very thick and wild whilst the roots around the sides are growing outwards and air pruning themselves naturally. You only want to snip away at the new growing tips and should avoid stressing the cannabis plant too much during its’ early days.

Rhizosphere Bacteria Stimulate Cannabis Plant Root Development

The left side of this root is healthy, but the right is even healthier. The difference is that the right side is being helped by beneficial bacteria. Read our article about beneficial bacteria and learn how to boost your plant’s root structure even more!

How Big Should My Pots Be For Air Pruning?

The wonderful thing about air pruning is the ability to manipulate the root zone to grow how you want it to. Starting off in a very small air pruned pot can actually develop a stronger thicker root base than growing normally in a large pot! The start of the prune is the most important so having a 10 cm air pruned pot can be perfect for the first three weeks. You need to have a strong root system so when you finally repot, your stem will be able to grow 5 to 10 cm wide. I would recommend finishing in a 15 litre sized air pot. This way your cannabis plant won’t need the biggest pots to be able to drink and drink all day long.

small fabric cannabis plant pot

Small fabric pots are ideal for developing a strong, healthy root ball

Trees are often grown in huge fabric pots as this is the ideal environment for a tree to really establish its’ roots. In fact, many of the recent advances in cannabis cultivation are derived from tree biology.

The 4 Inch Rule

A brilliant tip for those who want to grow a monster cannabis plant and are not too impressed with their current yields has been nicknamed “the 4 inch rule”. This rule advises to start with a 4 inch (10 cm) rockwool cube or coco expandable block. You can also buy some felt and make your own 10 cm square pots. The idea behind this is to max out the root zone in the first 10 cm to boost root development when you transplant the 10 cm thick root zone. An air pruned and well-developed root ball will make your plants more stress resistant and will make transplanting them much more reliable. If your cannabis plant is not totally filling the pot then you need to wait longer for it to be a solid square of white thick pointy roots.

4 inch rule for monster cannabis plants

This plant will explode as soon as it gets more space!

You can also have great success air pruning and filling out a 5 cm (2 inch) rockwool cube or fabric pot. This leads to well developed, thick stems and will boost your yields. Combining air pruning and the 4 inch rule will take your cannabis plant to another level!