You may have walked past a bottle of 3% food-grade hydrogen peroxide at the chemist (pharmacy) or the local grocery store and never even thought twice about it. It’s a staple. Not only is hydrogen peroxide a lifesaver when it comes to fighting an infected tooth or treating a cut, but it also has lots of great benefits and uses when applied to your grow room.
From cleaning your work tools, pipes, and hydroponic systems, killing pathogens and bacteria, accelerating seed germination, and as a general disinfectant…hydrogen peroxide can do it all! So, let’s delve deeper into the advantages of using hydrogen peroxide (H202) in cannabis cultivation and how this cheap and easy-to-make solution is a game changer.
Key takeaway: Uses for Hydrogen Peroxide in Cannabis Cultivation
The Many Uses for Hydrogen Peroxide in Marijuana Cultivation
Can I spray Hydrogen Peroxide Directly onto Soil or Mediums?
Is it Beneficial to Use Hydrogen Peroxide in Hydroponic Cannabis Systems?
How to store and handle Hydrogen Peroxide in your Grow Space.
Key takeaway: Uses for Hydrogen Peroxide in Cannabis Cultivation
Clean your grow tent / grow room, including the walls, corners, and floors.
Make a foliar spray to deter insects and flies to enhance plant health.
Add 3-10% into hydroponic systems for a healthy root system.
Treat algae and use it to prevent it from growing back.
Mix with distilled water to accelerate the germination rate of cannabis seeds.
Encourage old and difficult-to-crack seeds to open.
Spray the spores of powdery mildew that grow on the plant’s leaves.
Fight off bud rot and disinfect the part of the bud that has been infected.
Nurture roots with more oxygen and a gentle bubble bath.
Guarantee a deep clean in hydroponic systems, pots, drip lines, and drip stakes.
Disinfect gardening tools to remove organic matter and prevent fungal infection.
The Many Uses for Hydrogen Peroxide in Marijuana Cultivation
It can be counter-intuitive for a new grower to incorporate hydrogen peroxide in their grow room; however, there is a time and place for everything. I often think,” When in doubt, get the peroxide out.” That covers disinfecting your equipment, speeding up the germination rate of slow and stubborn seeds, battling root rot, pests, and algae forming on the growing medium’s surface, and giving clones inside a hydroponic bubbler a helping hand.
The best defense is a good offense, so make sure the plants can’t get pests in the first place!
Hydrogen Peroxide: A Great General Disinfectant When Growing Marijuana
Hydrogen peroxide (H202) is an excellent product for cleaning grow spaces. If you are using a tent in your bedroom, converted cellar, or attic or are learning the ropes indoors with a stealth grow box, then washing the walls, surfaces, and floor down with hydrogen peroxide (and bleach) will ensure your grow space is as sterile as can be.
Hydrogen peroxide can be poured into a spray bottle or applied directly.
3% food-grade bottles are available in many shops and local supermarkets.
Making your own solution is easy and will last a long time. (more on that later)
Make sure to clean your entire grow room, so no spores or pests are present. The cleaner the better!
Speeds Up Your Cannabis Seed Germination
There are various ways to germinate seeds; one of the old-school methods is to use a cup of water. Older or stubborn seeds might need extra encouragement to pop open, and hydrogen peroxide is one of the easiest ways to give the seed a push. For many growers, hydrogen peroxide helps accelerate the germination process, which can only be a bonus! Check out this article on germinating weed seeds with hydrogen peroxide for further clarification and better insights.
Using hydrogen peroxide keeps the water well oxygenated, ideal for germination.
Old seeds that are difficult to crack and germinate can benefit from peroxide.
Adding 3% hydrogen peroxide to a small water bottle is a treat for germination.
Root-Rot Free Cannabis Plants with H202:
When growing cannabis using a hydroponic method, monitoring your roots is a challenge. Unless you are growing in a Deep Water Culture system (DWC), where DWC buckets allow quick and easy access to the root zone, it can be difficult to know if your roots are in bad shape or suffering from root rot. Therefore, I recommend adding H2O2 to your reservoir for hard-to-access substrates such as coco coir, hydroton, and rockwool.
The primary culprits for roots becoming infected in the first place are overwatering, cold temperatures, and low oxygen levels around the roots. These factors combined can cause an otherwise healthy root system to become infected. If not treated quickly, they can lead to a world of problems. Hydrogen peroxide can treat root rot by directly attacking the pathogen, turning those precious roots into shiny, healthy white.
Root rot slowly turns the roots of a plant to a dark brown and frail root mass.
Soil can contain pathogens that come into contact with roots, infecting them.
Hydrogen peroxide will kill root rot easier in deep water culture than in soil.
Root rot can take various nasty forms. An example is visible above, which clearly shows root rot on a marijuana plant.
H202 against Bacterial And Fungal Infections:
An airborne pathogen is one that enters a growing space through ventilation and attacks the plants. In this case, we are talking about mold and powdery mildew, two highly problematic infections. Often, the cause of mold or mildew will be poor ventilation and high and fluctuating humidity levels. Hydrogen peroxide can clean the infected area; however, totally preventing the pathogen is impossible without amending the environment first.
Powdery mildew will attach itself to the leaf tissue of a cannabis plant and spread.
Mold and powdery mildew can easily spread, especially the more you touch your plants.
It is essential to fix the environmental issues causing the infections in the first place.
Powdery Mildew can be devastating for your weed plants, so act immediately once you spot the first signs!
There are other options to prevent pests and fungi on your cannabis plants. We actually sell Robert Bergman’s Plant Protector in our store, which you can find right below!
Bergman’s Plant Protector
Protect your plants from diseases and harmful pests.
Consists of three 20 ml bottles
Enough plant protection system supplies for up to 20 plants
Suitable for soil, hydroponic and all other grow mediums
H2O2 Gives Cannabis Roots More Oxygen
Hydrogen peroxide can provide a gentle bubble bath for the root system of a marijuana plant and, as a result, can increase root mass. When providing your plant’s roots with hydrogen peroxide, do so sparingly and only when needed; for example, fighting root rot, insects living on the soil’s surface, and treating algae. Don’t abuse it, as beneficial microorganisms, beneficial insects, or predators (the good kind, like lacewings, minute pirate bugs, mite midges, ladybugs, and spider mite rove beetle) within your growing medium will suffer and die out.
H2O2 Helps With The Cloning Processes of Cannabis
I personally love to use 3% hydrogen peroxide for cloning and keeping the bubblers clean and sterile, as well as accelerating the cloning process. A bubbler is a miniature version of a deep-water culture / aquaponic setup that allows freshly taken cannabis clones to sit in an aerated chamber that has the ideal moisture level to encourage root growth. I do not recommend using hydrogen peroxide when cloning conventionally (using coco or rock wool jiffy cubes). Doing so may cause the jiffy to become too wet, affect rooting, and potentially promote pathogens.
Washing your scalpel or scissors with hydrogen peroxide will keep them sterile.
Bathing freshly taken clones in a bowl of 3% peroxide will wash away insects and dirt.
Hydrogen peroxide can be added to the reservoir of an aeroponic / DWC cloner.
Add hydrogen peroxide to the reservoir of an aeroponic or DWC (Deep Water Culture) cloner to enhance the survival prospects of the plants. Ensure that it is administered in a way that optimizes plant health and growth.
H2O2 As a Pest Control For Your Cannabis Plants
Nothing is more frustrating as an indoor grower than watching tiny flies fill your tent and drive you crazy. At the same time, you are noticing there is more and more leaf damage each day you check on your plants, only adding to your anxiety levels. When used as either a foliar application or applied directly to the top layer of a growing medium, hydrogen peroxide can kill most of the pests, including eggs and any harmful pathogens they may be carrying.
If you use predators such as lacewings, minute pirate bugs, mite midges, ladybugs, and spider mite rove beetle to combat your insect problem, avoid using hydrogen peroxide and allow the predators and Mother Nature to keep a balance. Unfortunately, the peroxide will kill insects of all kinds, including the beneficial soft-bodied insects, wasting time and effort.
Insects living beneath the top layer of the medium will become deterred and leave.
Hydrogen peroxide is an excellent foliar spray to remove harmful insects and eggs.
Tiny flies can be frequently sprayed with a mild peroxide solution until they are all gone.
Use a spray bottle with hydrogen peroxide (H202) to mist cannabis plants. This helps protect them from problems and makes them healthier and stronger.
H2O2 Prevents Algae Growth on Hydroponic Equipment and Substrate
Algae that grow on top of soil or hydroponic systems using rock wool or coco can stand out like a sore thumb, and for those who enjoy working in a spotless and sterile environment, algae can be a pain. In all honesty, it is the one thing that causes hardly any damage to the actual plants; however, it will be a breeding ground for pests and microbial life. It can also clog your systems.
You can apply peroxide to algae growth. It will not take long to aggressively bubble and dissolve the algae.
Cube caps are designed to cover the tops of rock wool cubes and also prevent algae.
Algae treated with hydrogen peroxide is easily removed after a few applications.
Apart from attracting insects, algae have no real negative effect on plant growth.
H2O2 is Perfect for Cleaning Your Hydroponic Systems
Every grower loves a deep clean; if not, you should! Every hydroponic setup requires a thorough washing. That means tubing, drip steaks, net pots, air stones, tanks, and top trays or lids all need a bath. Soaking the parts of your hydroponic system will let salts or nutrients break away and wash out. Generally, a diluted solution with a 3% to 10% peroxide ratio is ideal for a deep clean, but always wear gloves and goggles to protect your hands and eyes.
Certain enzymes (like Pectinase) are also popular amongst hydroponic growers during the cleaning stage.
I like combining enzymes, peroxide, and bleach to ensure a true deep cleaning.
Organic nutrients that have built up inside pipes will bubble away and break down.
How to Use Hydrogen Peroxide on Cannabis Plants?
There are pros and cons when it comes to using hydrogen peroxide on marijuana plants. However, when used as a general disinfectant, foliage spray, or a peroxide soak for an infected root zone in deep water culture, hydrogen peroxide is a gift from the canna gods! As always…safety first, so keep your gloves and safety goggles handy when handling H202!
What Concentration of Hydrogen Peroxide Should I Use When Growing Cannabis?
3% foliar spray as a deterrent for flies and insects.
3% foliar spray to fight off powdery mildew.
3% foliar spray to prevent mold from spreading.
10% ratio in deep water culture to kill root rot.
A table with H202 dilution ratios for different uses
Step-by-step Guide on How to Make Diluted Hydrogen Peroxide
Making a customized diluted hydrogen peroxide solution is very simple and will save you from buying 250 ml-sized ones from the local shop. This step-by-step guide is based on producing a liter spray bottle with a 3% ratio of peroxide, which you will use as a general disinfectant spray or foliar application. You will need to start with the following list:
1 liter bottle of 10% hydrogen peroxide
1 liter of distilled water
1 liter sized bottle/spray bottle
Protective gloves
Eye protection
Sticker label
STEP 1 – Safety first! Protect your hands and your eyes with goggles.
STEP 2 – Take your liter bottle/spray bottle and fill it up with distilled water to the top
STEP 3 – Now you will measure 30 ml of the 10% hydrogen peroxide solution
STEP 4 – Pour the 30 ml of peroxide into the bottle of distilled water and mix.
STEP 5 – Write “ 3% hydrogen peroxide ” on the label and clearly place it on the bottle.
Keep the information above close, or write them down on paper or a noteblock.
Can I spray Hydrogen Peroxide Directly onto Soil or Mediums?
The answer is yes; however, you must remember that hydrogen peroxide kills good bacteria, fungi, microorganisms, and predatory insects. Spraying directly onto coco, rock wool, and hydroton to kill algae will not have any adverse effects as these are inert growing mediums and do not contain beneficial microorganisms.
Soil growers experiencing pests or root rot will ultimately kill all microbial activity – including the beneficial microbes when treated with hydrogen peroxide.
Is it Beneficial to Use Hydrogen Peroxide in Hydroponic Cannabis Systems?
Yes, a hydroponic system does not use beneficial microbes and fungi, that means you can add hydrogen peroxide to your reservoir. Combined with the dissolved oxygen the system’s air pump provides, the root system will thrive, encouraging fast growth and vibrant plants. In fact, hydrogen peroxide can be used from the earliest stages of cloning in a bubbler until harvest to ensure root rot is kept at bay.
On the left, thick, white, and well-spread roots signify a healthy plant with good nutrient absorption. The right side displays discolored, slimy, and weak roots, pointing to a plant likely struggling with nutrient uptake problems, possibly due to root rot or disease.
How to store and handle Hydrogen Peroxide in your Grow Space.
Storing your different bottles of peroxide solutions correctly is important. Keep your bottles in a cool, dark place like a cupboard or cabinet. Try to get into the habit of labeling each bottle you make to avoid using the wrong bottle or spray. Making a new solution every harvest is recommended. Remember, hydrogen peroxide is a powerful oxidizing agent that can burn and cause irritation, so once again…wear rubber gloves and goggles, ladies and gentlemen!
Top tips to Use Hydrogen Peroxide like a Professional
Top tip #1 – Clean clones with peroxide
Working with clean and pest-free clones is essential when the goal is to grow a lush garden, so a great tip is to add 5–6 drops of 3% hydrogen peroxide to a bowl of water. Dip your freshly taken clones into the water and watch how all the dirt, dust, and insects bubble to the surface.
Top tip #2 – Keep out of direct sunlight
Cannabis growers should keep plenty of things out of direct sunlight – cannabis buds, nutrients, seeds, IMO cultures, and, you guessed it…hydrogen peroxide. My tip is to keep your peroxide solutions labeled and stored in a cool, dark cupboard.
Top tip #3 – Protect yourself
I can’t stress how important it is to look after yourself in the grow room, especially when handling concentrated hydrogen peroxide. My tip is to cover your eyes with goggles and always cover your hands with latex rubber gloves before making your own solution.
Matthew DeBacco is a Professor of Agronomy (MS) as well as Plant Pathology and Horticulture (BS), who teaches several courses on the Horticulture of Cannabis at the Department of Plant Science and Landscape Architecture at the University of Connecticut.
Be sure to like and subscribe to his channel: https://www.youtube.com/@DeBaccoUniversity
My final thoughts on using Hydrogen Peroxide
If you are a beginner grower, all you must know is that hydrogen peroxide kills all microbes. So, if you are a super soil enthusiast, you may want to use products such as effective microbes (EM1) to combat soil pathogens and find an organic pesticide. On the other hand, if you are a hardcore hydroponic grower who is adamant microbes and fungi are simply not for you, then hydrogen peroxide has many benefits.
You can do a lot with just a few 250 ml store-bought bottles of food grade, 3% hydrogen peroxide around. Tackle everything from post-harvest deep cleaning to thoroughly washing your drip lines, stakes, air stones, and pots to germinating stubborn seeds. It is well worth the cheap investment. If you want to take things a step further and create your own hydrogen peroxide mixture, buying a liter of 10% peroxide will last a long time.
It is also worth considering that sourcing higher concentrations, (such as 35% hydrogen peroxide) may be slightly more challenging!There is nothing more exciting than combining science and plants. Buy yourself some hydrogen peroxide, read Robert Bergman’s Grow Bible, and develop an awareness to identify when you may need to use hydrogen peroxide in the first place. Don’t forget that hydrogen peroxide is only a preventative and not the cure for everything, and knowledge is a grower’s true power.
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