The importance of giving cannabis plants fresh air

The importance of giving cannabis plants fresh air
Max Sargent

Growing cannabis requires several key environmental conditions in order to be successful. One of these is a steady supply of fresh air to replenish carbon dioxide and maintain humidity, temperature, and more. Though essential, ventilating a grow is fortunately fairly easy. Here's how to do it.

Like humans, cannabis plants require a few key factors for their survival. Light, water, nutrients, and air are non-negotiable when it comes to growing weed. Remove any of these, and your plants won’t last long.

In this article, we’re talking about fresh air. Why do cannabis plants need it, and how can you ensure they get enough of it? Fortunately, the solutions are varied and generally simple, and have incredibly beneficial effects!

Why do cannabis plants need fresh air?

The importance of giving cannabis plants fresh air

Fresh air is one of the crucial elements of a successful cannabis grow—and one of the more easily overlooked. When we begin growing weed, it’s easy to focus on lights, nutrients, space and so on, and forget that good air circulation and a steady supply of carbon dioxide is also crucial to a healthy grow.

In nature, plants need their oxygen and carbon dioxide supplies constantly refreshed in order to survive and perform photosynthesis. Photosynthesis is the process by which plants produce the carbohydrates they need to feed themselves. The chloroplasts of plants—cells filled with green chlorophyll, which gives plants their colour—absorb blue and red light waves. The energy from these waves is then used to synthesise glucose from carbon dioxide.

During this process, the water loses electrons, which are then added to the carbon dioxide. What remains of water once it has lost electrons is oxygen, a waste product, which is then released by plants and emitted into the atmosphere—giving the planet the plentiful supply of oxygen necessary for almost all life to exist.

All of this is to say, without airflow, cannabis plants would be unable to produce energy, and therefore would not be able to exist!

The importance of proper air circulation

The importance of giving cannabis plants fresh air

The above process isn’t the only reason cannabis plants need sufficient air circulation. Maintaining proper airflow is perhaps the best way to ensure a stable, beneficial environment for your plants—taking away the “bad” and bringing in the “good”.

Refreshes carbon dioxide

Just to reiterate, good airflow will keep your plants happily breathing. Imagine you’re trapped in a small, sealed tent. Over time, as you breathe, oxygen levels will dip and carbon dioxide levels will rise.

For a cannabis plant growing in a tent or room, this happens in reverse; it absorbs carbon dioxide and releases oxygen. Eventually, levels of carbon dioxide will dip so much that the plant is unable to photosynthesise properly, stunting its growth.

For this reason, supplying your weed plants with fresh air and ample carbon dioxide on which to feast is a necessity.

Controls humidity

Airflow helps to control and maintain a good level of humidity. While some humidity is important for the growth of cannabis plants, too much can be very detrimental.

Water absorption is a passive process for plants. When they lose water through the stomata (pores) on their leaves, water is drawn up through the plant, which leads them to pull water (and some nutrients) in from the soil via their roots. This process of transpiration is important, as it means plants stay properly hydrated and their processes occur at a healthy rate.

If humidity is too high due to a lack of CO₂-rich air, then transpiration can slow, meaning plants struggle to absorb enough water.

Controls mould and pests

Stagnant air can slow plant growth while also harbouring pests and creating the perfect environment for mould to thrive. Fungal and bacterial growth can be really bad news for a cannabis grow—think bud rot. Especially as crops mature and grow more leaves and flowers, high humidity can be a real problem, and the chances of some sort of infection or infestation taking hold become much higher.

Keeping the air moving helps to prevent these pathogens from growing and flourishing.

Removes heat

Obviously, cannabis plants prefer fairly warm environments. But if things get too hot, then not only does this pose a risk to the growth of your plants, but it can even cause fires—which you definitely don’t want. Therefore, removing excess heat from your cannabis grow is very useful for the health of your crop, as well as yourself and those around you.

Aside from safety concerns, removing stale, hot air and introducing fresh air into the grow space will help to circulate heat, keeping temperatures stable and useful for plant development.

How to introduce fresh air into your cannabis grow

Removes heat

So, now that you’re informed on the importance of fresh air when growing cannabis, you need to know how to introduce and maintain it.

It’s important to note that simply having a fan blowing inside a sealed grow room won’t refresh the air sufficiently. It may have some benefits, but the grow tent or room will need to be opened, fairly regularly, in order to achieve proper circulation.

Better yet; you can create some kind of air exchange system.

Exhaust system

Installing an exhaust system may sound like a lot, but it can be incredibly beneficial, in several ways.

An exhaust fan removes stale air from the grow tent while an intake fan brings in fresh air, controlling humidity, temperature, and carbon dioxide levels. It’s best to instal an exhaust system before you start growing, rather than waiting until you decide it’s a necessity. In order to use an exhaust fan, you’ll need a grow tent with a strong-enough skeleton to hold one. Otherwise, if using a grow room, you’ll need to securely rig it up.

A second benefit of an exhaust system is that you can fit it with a carbon filter, which can help to eliminate the odour of your grow. This can be very beneficial when it comes to keeping the neighbours happy!

Oscillating fan

For smaller, hobby grows, a simple oscillating fan can suffice. Moreover, young cannabis plants benefit from a gentle breeze as it helps them to strengthen their stems.

If you’re going to use a fan, then there must be some way for air to exit and enter the growing space. If it’s sealed, it won’t work. It’s possible to have the fan blowing out of an opening, with a second opening on the other wall where fresh air can come in.

Open the greenhouse

If you’re growing in a greenhouse or polytunnel, then there’s a pretty simple solution—open it! There’s no need for a fancy ventilation system if you’re using this kind of growing space; just open the doors (and walls) and allow the air to exchange naturally.

Moving air in and out of greenhouses is really important; anyone who has ever been inside one will know they can get very hot and humid. If managed properly, then this is also their great benefit.

Grow outdoors

If you grow cannabis outside, then you don’t even need to concern yourself with ventilation and air exchange. Your plants will be exposed to constant air circulation no matter what. Short of freak weather events, there’s little danger of the humidity or temperature rising so high that your plants struggle to grow.

Regarding pests and disease, outdoor growing is a double-edged sword. If the weather is good, then mould and bacterial growth tends to be low. However, if you have a damp spell, then it’s much easier for these pathogens to take hold, and there’s not so much you can do to influence the environment. Moreover, insect infestations are much more likely when growing outdoors, so take this into account.

Cannabis plants need to breathe too

Grow outdoors

It can be really easy to overlook the importance of air circulation and exchange when setting up a grow. However, without it, a lot of the effort you put into the rest of your operation will be wasted.

Whether excess humidity prevents your plants from transpiring, temperatures get too hot for plants to grow properly, or carbon dioxide levels drop too low, poor ventilation can damage your grow and reduce your final yield in numerous ways. And if you find bud rot, it can ruin the whole crop right at the end of the growing cycle.

So, with that in mind, ensure adequate ventilation in your cannabis grow—you’ll thank yourself down the line!

Max Sargent
Max Sargent

Max has been writing about cannabis and psychedelics for several years now. With a strong belief that an open, honest attitude toward drugs and drug policy can improve the lives of many, he seeks to offer insightful and developed opinions on the subject.