Does hydrogen peroxide help with germination?

Growers who have handled hydrogen peroxide before know how potentially dangerous it is for plants. In high doses, it can cause cell damage. But, H2O2 is something that plants also produce during photosynthesis. It acts like a hormone that regulates growth and development.

In fact, H2O2 may potentially speed up the germination process and help your seedlings’ growth and health. If you’re curious to know how to germinate weed seeds with hydrogen peroxide, our step-by-step process will help you go about it.

Should you soak your weed seeds in hydrogen peroxide?

So long as it’s a diluted solution, soaking seeds in hydrogen peroxide is a great way to speed up germination. It’s also a good way to sterilize your seeds and remove any bacterial or viral pathogens. But you mustn’t soak your weed seeds for too long, or your seeds may decompose in the solution.

How does hydrogen peroxide help with germinating seeds?

Hydrogen peroxide is a chemical compound that acts like hormones for your plants and seeds. In plants, they regulate growth and development in the roots. For seeds, H2O2 triggers physiological processes like germination to occur faster(1). Another way that H2O2 speeds up germination is by cracking the seed’s outermost covering. Because seeds need water and oxygen to kickstart germination, breaking their seed coat allows for more of it to be absorbed by the seed.

You can also use H2O2 to germinate old seeds that have developed a harder seed coat over time.

Besides speeding up the germination process, soaking cannabis seeds in hydrogen peroxide also sterilizes them. In fact, it’s a better solution for your seeds and far safer than aggressive chemicals like bleach(4).

However, it’s critical that you don’t soak your seeds in pure hydrogen peroxide. The concentration of the hydrogen peroxide (water to H2O2 ratio) can make the difference between it being beneficial or detrimental. Too much H2O2 will damage your plants’ cells or kill your seeds. Ideally, use a 1% H2O2 solution; this is enough to show the best results for cannabis seed germination (3).

Find a step by step germination guide in Robert’s Grow Bible below.

Does H2O2 speed up the germination process?

Yes, H2O2 does speed up the germination process. It is a signaling molecule that triggers physiological and biochemical processes in your cannabis seeds, which then induces germination. Additionally, H2O2 is regarded as one of the most stable signaling molecules for cannabis (1). Unlike other compounds, H2O2 requires a specific enzyme to decompose(5), making it ideal for creating seed-soaking solutions.

What happens if you use too much hydrogen peroxide?

When soaking seeds in water and hydrogen peroxide, it’s common to make mistakes around the concentration levels. Note that 10% hydrogen peroxide is the concentration for weed killer, and it will also kill your plants (6). The recommended solution is 1-3%. Any solution that contains more than 3% can do more harm than good for your seeds.

stirring peroxide into a cup for seedlings

How long should you soak your seeds in hydrogen peroxide?

We recommend that you only soak your cannabis seeds in the hydrogen peroxide solution for no more than 12-24 hours(4)(1). This is because your seeds will usually  show signs of germination around this time frame. To keep your newly germinated seeds from drowning and decomposing, don’t go over 24 hours. This would not be the case if you were soaking your seeds in water alone.

What is the ratio of water to hydrogen peroxide to use for seeds?

One of the most important things to take into consideration when making a hydrogen peroxide solution is the concentration. H2O2 comes in different strengths, and each one requires different amounts of water to dilute it into a solution that’s safe for soaking weed seeds. This chart details the ratio of water to H2O2 needed for making a soaking solution for your seeds.

Amount of water3% H2O235% H2O2
1 cup1 and ½ tsp.7 to 10 drops
¼ gallon2 tbsp.½ tsp.
1 gallon½ cup2 tsp.
5 gallons2 and ½ cups3 tbsp. and 1 tsp.
10 gallons5 cups6 tbsp and 1 tsp.
20 gallons10 cups¾ cups with 1 tbps. and 1 tsp.

Can you germinate older seeds with H202 (hydrogen peroxide)

It is certainly possible to germinate older cannabis seeds with hydrogen peroxide. The only issue with germinating old seeds is their harder seed coat(11). You need to crack that tough seed coat to germinate them, which is possible by using H2O2. You won’t need to make a higher concentrated solution for it either. The same 1% H2O2 solution you use for regular seeds is enough to germinate older ones(3). So if you have a bunch of old seeds you didn’t find the time to sow, don’t just throw them away. They may still be viable.

But, it’s only possible to germinate old seeds if they were stored properly. Just like with storing buds, if you don’t give your seeds the right conditions, they won’t last. For more on storing your seeds, read the article, how to store cannabis seeds. Or if you don’t trust you old seeds, check out collection of high yield marijuana seeds today!

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How to use hydrogen peroxide for germinating marijuana seeds

Disinfect growing medium

Besides using hydrogen peroxide to soak your marijuana seeds, you can also use it to disinfect your growing medium by applying the diluted solution as if you’re watering. Doing so eliminates harmful fungi like fusarium from soil-growing mediums and increases seedling growth in plants(7). Applying H2O2 on soil has the added benefit of remedying heavy metal-contaminated soil(8).

hydrogen peroxide germination process for seedlings

Seed sanitization

Because of hydrogen peroxide’s oxidizing properties, it is a good disinfectant that removes bacterial and viral pathogens and stops fungal infections. It’s the best solution if you want to sterilize your seeds. Other alternatives like mercuric chloride or bleach require additional washing of your seeds(4). For this method, soak your seeds in a 1% solution and let them sit for 12-24 hours or until most seeds have germinated.

Faster germination

Like sanitization, use hydrogen peroxide for faster germination by soaking your seeds in a 1% solution for 12-24 hours. H2O2 can speed up the germination process in seeds because it acts as a trigger for germination, which would otherwise take twice as long if you were to soak them in water(1). In older seeds with thicker seed coats, H2O2 breaks open the hardened outermost cover, allowing more oxygen and water to be absorbed by the seed.

Increased cannabis seedling root development

Promoting root development is another benefit of using hydrogen peroxide on your cannabis. Watering with your H2O2 solution increases O2 concentration in the soil, which increases nutrient and water uptake and has a positive effect on root growth(9)(10). 

cannabis seedling root development

Fight off fungus infections

In the same vein, watering your cannabis with your hydrogen peroxide solution helps fight off fungal infections in your plants, particularly in its roots which play a considerable role in increasing root development. It’s important to note that you need to be careful with how much H2O2 you introduce to your cannabis, which is where the chart will come in handy.

But with that said, you don’t have to trouble yourself with all of this. Unless you just want to salvage some old seeds you forgot to plant, you’re better off purchasing high-quality seeds from ILGM – they’re guaranteed to germinate. You can also check out our germination instructions for more information.

FAQs about using hydrogen peroxide with cannabis

Can you treat root rot with hydrogen peroxide hydroponics?

Yes you can. Outside of cutting off the damaged parts, you can use a mixture of hydrogen peroxide and water to treat root rot in your cannabis plants.

Should you dilute hydrogen peroxide solution when using it for germination?

When using hydrogen peroxide for germinating cannabis seeds, you must dilute it before you soak your seeds in it. Undiluted H2O2 will only damage your seeds.

Does H202 help with mold on cannabis plants?

Spraying your cannabis plants with a diluted hydrogen peroxide solution can help reduce the likelihood of mold appearing. However, it’s more of a preventative than a remedy. It won’t help much if your plants are already infected with mold.


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Mr Chris Gardner

Botanist and academic

Chris Gardner is a botany buff with years of experience in agriculture and graduated with a Bachelor’s degree in Science an ... See profile

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