Why use Hydrogen peroxide for plants? This common household first aid and cleaning agent is also AMAZINGLY helpful for plants. It benefits both garden and houseplants. But in this post we focus on your houseplants.
What is hydrogen Peroxide? Just regular ole water. Plus ONE extra molecule of oxygen. The chemical formulation is H2O2. It’s that extra oxygen molecule that gives us a powerful oxygenator so useful in the home and garden.
Is Hydrogen Peroxide Good for Plants?
Is hydrogen peroxide safe for plants? Hydrogen peroxide occurs naturally in Rainwater. It is perfectly safe for plants when properly diluted and used in moderation.

Adding hydrogen peroxide to water promotes better growth in plants and boosts roots ability to absorb nutrients from the soil. Diluted 3% peroxide adds needed aeration to the soil of plants and helps control fungus in the soil.
For indoor plants use 3% peroxide rather than stronger concentrations. It is safer and easier to use than more concentrated solutions.
What are the Benefits of Hydrogen Peroxide?
This powerful oxygenator helps plants in several ways. Here are three Major benefits for your housplants.
Hydrogen Peroxide…
- Encourages and supports Plant growth by supplying oxygen into the soil. Plants absorb more nutrients and grow faster.
- Eliminates soil fungus spores and molds. In fact it can sterilize soil of all pathogens.
- Kills fungus gnats when used as a soil drench and deters sap sucking insects when regularly applied as a leaf spray.

How much 3% Hydrogen peroxide Do I Use?
Use 3% hydrogen peroxide for plants in these dilutions to help your plants:
- For misting Indoor plants mix 1 tsp./ cup of water. This improves aeration to your plant and deters fungus on leaves and soil. The ratio here is one part 3% hydrogen peroxide to 48 parts water.
- To help kill pests on the plant leaves like Aphids, spider mites and other sapsuckers use the misting solution above.
- Ratio of 3% hydrogen peroxide to water is 1 part h202 to 8 parts water. This is a solution for example of 1 pint Hydrogen peroxide/gallon of water. It is safe to pour as a drench around your plant roots to sanitize the soil of fungus and other pathogens. Pour the solution into the plant pot around the roots and let the pot sit overnight to drain.
- Mix 1 1/2 Tablespoons baking soda and 1 1/2 tablespoons 3% peroxide with 2 and a half gallons (approximately 9.46 liters) of water for a powerful homemade anti fungal solution that can be sprayed directly on the plant leaves. This is helpful in getting rid of powdery mildew and other leaf spot diseases.

To Help Fix Root Rot:
Applying Hydrogen peroxide aerates waterlogged plant roots . The improved oxygen circulation to plant roots can save roots in danger of root rot. And those in the early stages. Hydrogen Peroxide will kill the pathogens that cause the rot.
Drench the soil with 1 part 3% peroxide/ two parts water to kill off the bacteria causing the rot in your soil. Let the plant drain completely.
Waterlogged roots cause a Lack of oxygen to the roots. The roots will suffocate and eventually die. Hydrogen Peroxide properly applied can help.
This will also help immediately deliver much needed oxygen to the plant roots and kill off bad bacteria in the decaying roots.
I wrote a whole post on how to fix root rot and another on 7 reasons your plants has Yellowing leaves. We all run into these common overwatering problems in houseplants from time to time.

To Effectively and Safely Use Hydrogen Peroxide:
Hydrogen peroxide works very quickly… and then quickly breaks down. After it loses its oxygenating properties the benefits of using it are gone. SO you need to mix up your solution for your purpose and then immediately use it to gain the best benefits.
If you want to make a solution and keep it long term it must be stored in a dark water tight container in a cool place.
Never leave hydrogen peroxide where kids and pets can get into it.
At higher concentrations you should wear gloves when working with hydrogen Peroxide. At 3% the solution is safe for normal handling with your houseplants.
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Nick
Saturday 25th of March 2023
Hi Diane,
Thank you for the informative article. What would happen if you (accidentally) spray the plants (seedlings/plantlings) with 3% hydrogen peroxide directly? Didn't dilute it before spraying due to excitement :(
Please help, thank you! And have a nice day :)
yours sincerely,
Nick
Diane Williams
Monday 27th of March 2023
Hi Nick, Spraying the hydrogen peroxide directly on the plant is not a good idea. If you can directly following that accident I would spray the plants liberally with water to wash it off. If the plant is going yellow...it may be too late. Hopefully they will make it through. My husband killed his pepper plants this way. Best of luck!
Kelly Beatty
Thursday 16th of February 2023
regarding the anti-fungal mixture of water, baking soda, and H2O2, which is it: 4 liters or 2½ gallons (because 4 liters is just a tad more than 1 gallon)
Diane Williams
Friday 24th of February 2023
The conversion of gallons to liters in the given solution is correct. 2 and a half gallons are equivalent to approximately 9.46 liters. The conversion factor for converting gallons to liters is 1 US gallon = 3.78541 liters. Therefore, 2.5 US gallons can be converted to liters as follows:
2.5 US gallons x 3.78541 liters/US gallon = 9.46353 liters
Rounded to two decimal places, the result is approximately 9.46 liters. So, mixing 1 1/2 tablespoons of baking soda and 1 1/2 tablespoons of 3% hydrogen peroxide with 2 and a half gallons (approximately 9.46 liters) of water should produce the correct concentration of the solution.
This is a powerful antifungal solution that can be sprayed directly on the plant leaves, But be careful here. My husband sprayed it on his (already sick and heavily infested with spider mites) pepper plants and they died. It is essential to mix the solution properly and apply it carefully to avoid any damage to the plant.
It is always recommended to conduct a small test on a small area of the plant to ensure that the solution does not cause any harm or discoloration. I hope this helps!
Nikki
Monday 6th of February 2023
Is there a H202 out there that is exactly 3% already or are you making it 3% by adding the water to it? I have only found it at around 70% to 100%.
Diane Williams
Sunday 12th of February 2023
Hi Nikki, 3% hydrogen peroxide is available on amazon, in grocery stores and pharmacies. It is sold as antiseptics for wound care in 3 % dilution. I hope this helps!
Alex
Wednesday 25th of January 2023
You state “2.5 gallons (4 liters)” but 2.5 Gallons does not convert to 4 liters
2.5 gallons (US) converts to about 9.5 Liters.
4 liters converts to about 1 Gallon (US)
These are very different ratios.
Which one is correct?
Thank you
Diane Williams
Sunday 29th of January 2023
Hi Alex, Thanks for pointing this out. I corrected the conversion. Use 9.5 liters or 2.5 gallons of water in this mix. Happy Gardening!
Brian
Wednesday 25th of May 2022
Hi There I’ve bee been onto a few sites after hearing about the benefits of using h2o2 on plants, which is fantastic. My problem is that I live in the UK and I’m not sure about the dilution ratios as they don’t specify if they’re using US or UK measures.e.g a US gallon is 6 pints and a UK gallon is 8 pints or 4.55 Litres. Could you please be a bit more detailed, thank you very much in anticipation. Brian
Kelly Beatty
Thursday 16th of February 2023
@Brian, a U.S. gallon is 8 pints as well.
Kelly Beatty
Thursday 16th of February 2023
@Brian, a U.S. gallon is 8 pints
Andy
Thursday 1st of September 2022
@Diane Williams,
Hi, your post of: ''Mix 1 1/2 Tablespoons baking soda and 1 1/2 tablespoons 3% peroxide for a powerful homemade anti fungal solution that can be sprayed on the plant leaves. This is helpful in getting rid of powdery mildew and other leaf spot diseases. Or a ratio or 1:1 whatever your volume needs.'' seems to suggest to spray it without dilution. Although many sites differ on dilution ratios none of them suggest that the combination of baking soda and hydrogen peroxide be used at full strength unless you are using it as a cleanser for non-plant items. Full strength can bleach.
Andy
Diane Williams
Wednesday 25th of May 2022
Hi Brian, Thanks for the question! I have updated this post and put the ratios in for you. This should work for whatever measurements you use. Best of luck!