A Full Guide To Treating Cannabis with Hydrogen Peroxide

Last Updated on: September 29, 2024

Hydrogen peroxide, chemically known as H₂O₂ is a controversial topic in the Marijuana growing community. Some growers swear by it, but some avoid it like the plague.

So what gives? Should you be using hydrogen peroxide to treat cannabis cultivation problems? Sure, you can, but it all boils down to using it appropriately and in the right concentration. 

In this article, we’ll share all you need to know about using hydrogen peroxide solutions to treat numerous problems when growing cannabis and how you can avoid some common mistakes when doing so! 

Key Takeaways

• There is no harm in using hydrogen peroxide (H2O2) to treat cannabis problems when done in the right proportion and frequency of application. 
• Many different strengths of hydrogen peroxide are available, but the standard product available for home antiseptic use comes in a 3% dilution. 
• Use this pre-diluted 3% mixture and dilute it further depending on what you’re using it for.
• H2O2 can disinfect the growing medium and protect the cannabis seeds, keep nasty pests at bay, treat root rot or slimy roots, treat water, and improve aeration in poorly aerated soil.
• When used excessively, it could hurt beneficial microbial in the soil.
• Peroxide is usually a quick solution to many problems but you’ll also have to tackle the condition at its source. 

Is It Okay to Use Hydrogen Peroxide for Cannabis Problems?

While growers often have varying results from using peroxide, one thing is undeniable, and that is that it can treat numerous conditions if used correctly. 

For example, H₂O₂ can become applicable to cannabis plants when:

• You want to disinfect your gardening tools and hydroponic systems.
• You want to oxygenate the soil.
• You want to control pests.
• You want to treat issues like root rot, slimy roots, and mold.

Indeed, it’s safe to use hydrogen peroxide on your marijuana plant for various reasons. However, while hydrogen peroxide can address symptoms, it’s also important to identify and correct the underlying cause of the problem, which may require adjusting the nutrient balance or other growing conditions.

Also, many new growers get the method of application wrong. When done incorrectly, it can negatively affect your plant. 

This circles back to knowing how the chemical itself affects cannabis plants. 

How does hydrogen peroxide affect cannabis plants?

Source: YouTube

The easiest way to explain how hydrogen peroxide works when it touches cannabis plants is by looking at its role in soil oxygenation and killing pathogens. This happens because of an enzyme called catalase found in plant cells.

When plant cells use energy, they make hydrogen peroxide. The catalase enzyme breaks down hydrogen peroxide into water and oxygen through this reaction.

2 H₂O₂ + Catalase →  O₂ + 2 H₂O

The bacteria that harm cannabis plants are anaerobic, meaning they cannot live in the presence of oxygen. 

So, when hydrogen peroxide is applied to a plant, the catalase enzyme in the plant’s cells makes oxygen, which stops these harmful bacteria from living.

H₂O₂ also kills bacteria thanks to its strong antimicrobial properties and can be used to sterilize gardening tools. 

Cannabis Problems And How To Treat Them Using Hydrogen Peroxide

Here are some common problems associated with cannabis plants and how hydrogen peroxide can be used to solve them: 

1. Root Rot

Unless you’re using a Deep Water Culture (DWC) system, where it’s easy to check the roots of cannabis plants, it can be difficult to tell if your roots are healthy or suffering from root rot.

Usually, root rot turns roots dark brown and frail. Even without looking at the root, you can tell that your plant is suffering from root rot by observing the following: 

• Burned tips or edges of leaves.
• Brown, bronze, or yellow stripes or spots on the plant can indicate various issues, including root rot, septoria, or calcium-magnesium deficiency. Some troubleshooting may be necessary to diagnose and address the problem correctly.
• Leaves turn partly or completely yellow and wilt while growth slows down.

Hydrogen peroxide helps treat root rot by attacking pathogens but it also harms beneficial bacteria in the rhizosphere. Re-inoculating the roots with beneficial microbes after treatment can be beneficial. 

While hydrogen peroxide won’t turn dead or sick roots back to white, it will promote new and healthy root growth.

You can add hydrogen peroxide to your reservoir to treat various substrates such as coco coir, hydroton, rock wool, and even soil or soilless mixes. This helps manage pathogens in environments where direct application may be challenging.

The reservoir acts as a vital hub in the grow room to provide water and maintain optimal conditions for your plants.

2. Fungal infections

Various pathogens, with fungal diseases as one of the most common examples, can cause infections that damage plants foliage, and flowers. Other fungal diseases include bud rot and powdery mildew.

These airborne pathogens can enter your growing space through ventilation and harm your plants. 

The powdery mildew attaches to the leaves and spreads.

Pro Tip: 

• Hydrogen peroxide can clean infected areas, but to prevent these infections, you also need to fix the environmental issues. You need to ensure your grow space temperature, humidity, light, and air circulation are not hospitable for pests and pathogens to thrive.

3. Pest infestation 

Pests like fungus gnats, shore flies, and mealybugs can infect your cannabis buds.

You can use hydrogen peroxide as a foliar spray or apply it to the top layer of the growing medium to kill pests, their eggs, and the harmful pathogens they carry.

You can regularly spray tiny flies with a mild Hydrogen peroxide mixture (1 part of the chemical with 10 parts water in a dilution ratio) until they are gone.

Pro Tip: 

• If you use beneficial insects like lacewings, ladybugs, and others to control pests, avoid using hydrogen peroxide kills these helpful insects alongside the harmful pests, hence it’s important to avoid using it.

4. Algae growth on hydroponic equipment

If you use a hydroponic grower and algae grow on top soil or the hydroponic systems, you can use the H₂O₂ chemical. 

Algae can cause significant problems to hydroponic cannabis if left unchecked, as they attract pests and microbes and can clog systems.

Once you apply hydrogen peroxide to algae, it will bubble and dissolve quickly.

Pro Tip: 

• You can use cube caps to cover rock wool cubes and prevent algae growth.

What Is The Right Dilution Ratio For Hydrogen Peroxide in Cannabis Plants?

The proper dilution ratio and method of application for hydrogen peroxide on cannabis plants depends on the intention or issue you’re looking to solve. 

We’ve illustrated it better in the table below: 

Intention	Proportion of H₂O₂	Frequency of App4–5tion
Oxygenation of root	10 ml of 3% peroxide per liter of water to the hydroponic system reservoir	From cloning up to harvesting, every 4–5 days
To kill Algae growth	3–10% peroxide as foliar spray	When required
Other issues caused by Fungus Gnats	Mix 1 part hydrogen peroxide to 10 parts water	Daily until the problem is solved
H₂O₂ foliar spray for maintenance	Add 1.5 ml of H₂O₂ per gallon of water	Every 3–5 days
For germinating weed seeds with hydrogen peroxide	To 1 liter of fresh water, add 3.5 ml H₂O₂ 10 vol./liter water, about 35 drops	Soak the seeds in the solution for no more than 24 hours (or for 12 hours, then use your usual germination method)
General disinfectant	10% peroxide combined with bleach	Post-harvest

Pro Tip: 

• You have to observe your plants and adjust the frequency based on their response. 
• 3% food-grade hydrogen peroxide chemical bottles are available in many shops and local supermarkets. You can get those to save you the trouble of mixing the H2O2 solution yourself at home. 

What’s the danger of using Hydrogen Peroxide on Cannabis Plants?

The main danger of using hydrogen peroxide on cannabis plants is that it will kill both harmful and beneficial bacteria in the soil.

Many growers don’t dilute hydrogen peroxide enough, which can be harmful because it kills beneficial organisms at high concentrations.

Water and hydrogen help to control all the gnat larvae and kill helpful microbial life. How can you prevent this? 

1. Mix 3% of the Hydrogen peroxide with water in a 1:2 ratio. This is safe for the roots and provides a significant oxygen boost.
2. After flushing with hydrogen peroxide, add new beneficial microbes (Azotobacter, Clostridium, and Frankia) to keep the rhizosphere healthy.
3. After the peroxide flush, sprinkle diatomaceous earth (DE) on top of the soil to prevent adult gnats from laying more eggs.

Cannabis Plant Problems You Shouldn’t Treat With Hydrogen Peroxide

Since it’s an organic solution, hydrogen peroxide may sound like a solution to many cannabis pests and other plant problems. But it’s a temporary solution to problems like root rot, not a permanent one. 

The oxygen the roots will receive from the hydrogen peroxide is short-lived. 

So it’s not an issue of what problems can’t be solved; it’s a question of finding a long-lasting solution to the problem you are dealing with. 

“Also, it’s best not to use hydrogen peroxide to treat the plant if your germination method involves beneficial organisms like beneficial bacteria or insects such as lacewings.”

Tips for Using Hydrogen Peroxide in Your Garden to Treat Your Cannabis Plants 

We’ve looked at various aspects of using hydrogen peroxide concerning your cannabis plants. But there are some tips you should also note for your safety. 

1. Never boil or heat hydrogen peroxide because it can become unstable and explode. 
2. Keep it away from any flames.
3. Store hydrogen peroxide in a cool, dark place, away from sunlight. Light can break it down, so it comes in dark brown bottles. 
4. Always wear rubber gloves when you handling concentrated hydrogen peroxide to avoid burns or skin irritation. 
5. If it gets on your skin, rinse the area thoroughly with water.

Hydrogen peroxide is a helpful chemical for cannabis growers thanks to its disinfecting qualities. 

If you’ve hesitated to use it because of concerns about its effects, just remember that it’s about using it at the proper dilutions and applications. 

While treating problems with your cannabis plants, always ensure they are getting the right nutrients. Supplying your plants with the right nutrients can prevent many of these issues. 

At Aussie Hemp Seeds, we offer nutrient packs to accommodate crops’ needs as they mature and blossom. You can also explore our collection of fast-growing high-yield seeds.

I hope you find this guide helpful.