The Benefits of Adding CO2 During the Cloning Stage

By Lee G Lyzit
Published: December 3, 2020 | Last updated: May 26, 2021 05:31:56
Key Takeaways

Are cannabis plants in the cloning stage too small to benefit from enriched CO2? Lee G. Lyzit doesn’t think so. He explains why using CO2 during the cloning stage reduces pathogens and gives young plants a better chance at survival.

Many indoor cannabis horticulturists are reaping the benefits of enriched carbon dioxide levels in their vegetative rooms and their blooming rooms. Increased CO2 levels can maximize the rate of photosynthesis and, in turn, increase the rate of growth.


It is common for growers who supplement CO2 to see not only faster growth, but also larger yields. When done correctly, and everything else is equal, a growroom enriched with CO2 will simply outperform a growroom without it.

However, while most growers agree that there are definite benefits of CO2 enrichment in the vegetative and blooming rooms, there is an ongoing debate about the benefits of CO2 in a cloning area.


Some growers argue that the plants in the cloning stage are too little to benefit from enriched CO2, while others argue all plants, regardless of size, benefit from CO2. CO2 enrichment during the cloning stage, when done correctly, can increase the speed at which a plant creates roots, as well as increase success rates by eliminating or reducing potential pathogens.

cannabis clone rooted in rockwoolFaster rooting means young plants can be transitioned into the vegetative stage and acclimated to a new environment sooner. Source: OpenRangeStock / Shutterstock


Faster Rooting with CO2

Increased CO2 levels in the cloning area are beneficial when supplied to the cuttings’ leaves. So, if a grower is using an aeroponic or mister-type cloning machine, the CO2 should be added to the area where the leaves are and not to the area where the roots are (or will be). When the leaves have access to enriched CO2 levels, photosynthesis can occur at a faster rate.

The sugars created in this process are important fuels that provide the cuttings with the energy they need for making roots. In other words, raising the CO2 levels increases the speed at which these valuable sugars can be produced.


If the sugars needed for energy can be produced more quickly, the cuttings can, in turn, create roots more rapidly. Faster rooting means young plants can be transitioned into the vegetative stage and acclimated to a new environment sooner. Generally speaking, the faster the clones can develop roots, the higher the overall success rate of cloning.

(Read also: Mastering CO2: Ideal CO2 Levels for Growing Marijuana)

Reduced Transpiration in Enriched CO2 Environments

One of the main reasons why cuttings are kept in a high-humidity environment is because, without a root system, the cutting’s leaves become the main source of water control and retention.

Without a high-humidity environment, the cuttings from some plant varieties would transpire moisture to the point of wilting, and possibly death, from lack of water. A high-humidity environment reduces the cutting’s need for transpiration and protects the cutting from losing too much moisture.

To better understand the relationship between transpiration and CO2, we can look at an enriched CO2 environment’s impact on the plant’s stomata. Plants absorb CO2 through the open stomata on their leaves.

Transpiration occurs when the stomata are open as well. As mentioned, transpiration leads to loss of water, which is another significant part of the photosynthesis process. So, to conserve water, plants will automatically regulate the amount of time the stomata are open.

(Read also: The Symbiotic Relationship Between CO2 and Ventilation)

When an indoor horticulturist enriches his or her cloning environment with CO2, there is more CO2 available for absorption when the stomata are open. In other words, the plant can absorb more CO2 while trying to limit water loss through transpiration.

Some experiments have shown that when provided with an increased amount of CO2, plants will not open the stomata as wide, thus reducing the amount of transpiration. This is a huge benefit for cuttings without roots in the cloning stage.

Any reduction in transpiration is a large advantage for rootless clones. Overall, increased CO2 levels will increase the efficiency of a plant’s water use which, for clones, can mean the difference between wilted foliage and good structural integrity.

Cannabis plant infected with powdery mildewCannabis plant infected with powdery mildew.

Increased Resistance to Molds, Fungi, and Bacteria

It just so happens that the ideal environmental conditions for cloning (warmer temperatures and increased humidity levels) are also the conditions conducive to many plant pathogens.

Powdery mildew, root rot, and grey mold are just a few of the nasty things that find the cloning area’s environment perfect for setting up shop. Enriching a cloning area with CO2 is one of the most effective and safest ways a grower can prevent pathogens from attacking the otherwise susceptible cuttings.

It is believed that CO2 is an effective anti-fungal due to its ability to alter intracellular pH levels. In other words, an enriched CO2 environment during the cloning stage can actually alter the pH of the leaf’s surface, making it impossible for particular fungi to become established.

A closer look at many of the products designed to treat or prevent molds in the garden will reveal that most of these products are effective because they alter the pH of the leaf’s surface.

When it comes to reducing pathogens in the cloning area, prevention is key. Enriched CO2 levels can prevent problems before they occur and allow a grower to increase his or her overall success rate.

(Read also: Sourcing CO2 for Your Indoor Garden)

Methods for Administering CO2 to Cannabis Clones

There are a few different ways a grower can increase the CO2 level in the cloning area. CO2 burners, compressed CO2 tanks, or passive solutions like bottles, bags, or pads, can all be rigged to enrich CO2 levels during the cloning stage.

However, too much of a good thing can be bad. When using a CO2 system designed for a large area, a grower should be cautious to avoid the CO2 levels getting too concentrated.

For clones, CO2 levels between 1,000-1,300 ppm should be the maximum. Levels above this can be counterproductive as the available oxygen gets displaced by CO2.

The roots (or potential roots) need oxygen (aeration) to develop and thrive. Growers who choose to use CO2 burners or compressed tanks with injector systems need to have a CO2 monitor/controller so the CO2 levels can be kept in check.

Perhaps the best solutions for administering CO2 to clones are the CO2 pads specifically designed for cloning chambers. These pads can be placed directly into a standard propagation tray and cloner dome and are activated by the humidity within (or when the clones are misted with water).

The CO2 pads are made from natural chemicals which, when exposed to humidity, begin to release CO2. Since the pads are made specifically for propagation trays and cloning, they are designed to release the correct amount of CO2 for that stage of growth.

(Read also: Return of the Cannabis Clones)

In fact, CO2 pads made for cloning propagation trays usually put the CO2 levels between 450-1,200 ppm. This level of CO2 is ideal for the cloning stage because there is enough to increase the rate of photosynthesis (creation of sugars) and prevent certain pathogens from establishing, but not so much that root growth will be inhibited.

Pads in the clone area may need to be replaced every few days to ensure a consistent level of CO2 throughout the entire rooting process.

Of all the stages of growth in a perpetual indoor garden, the cloning stage is the most difficult for horticulturists to master. When success rates in the cloning stage are suffering, the entire perpetual garden suffers.

This is why it is so important for horticulturists with perpetual gardens to have consistent results in the cloning stage. One of the best ways a grower can increase his or her success in cloning is to implement CO2. When done correctly, increased CO2 levels will give the plants the ability to create more sugars (fuel) at a faster rate.

With those sugars, the plants are able to produce roots more quickly. Regardless of the benefits brought on by faster rooting, the protective nature of CO2 enrichment is a good enough reason for horticulturists to add CO2 to the cloning stage.

The prevention of possible pathogens automatically increases success rates and eliminates potential glitches that could otherwise inhibit the flow of a perpetual garden. Considering the multifaceted benefits, the addition of CO2 in the cloning stage could be one of the most influential factors affecting the early stages of a perpetual garden.

Read more on CO2 supplementation


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Written by Lee G Lyzit | Grower, Writer

Profile Picture of Lee G Lyzit

Lee G. Lyzit has been involved in the cannabis industry for nearly 20 years. His passion for natural healing motivates him to learn as much as he can about the miraculous cannabis plant. Lee’s knowledge of cannabis gardening stems from his own extensive cultivation experiences and his past work as a hydroponic shop owner and manager.

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