What is Hydrogen Peroxide?
This is a colorless, sharp-smelling chemical which looks a bit like water. It is commonly used for household uses such as disinfectant and in cleaning products. It is rare to see pure hydrogen peroxide as it is most commonly used as a watered down solution.
It comes mixed with water which is typically 6% HP and the rest ordinary H20.
You may have heard of it as a hair bleach and peroxide is what is used by hairdressers to get a bright blonde hair color. It is used for medical problems like disinfecting small cuts or wounds and even treating boils or acne. It has a myriad of uses in household cleaning and it can even be used to kill mites and remove algae and scum from your home aquarium.
How Does It Work?
It is a very similar chemical composition to water and if it was in a sealed bottle you may even mistake it for water. And its effect on plants is actually quite positive.
But when it comes to gardening, this solution on plants does so much more than just simple water. Even though this is a chemical compound, it is actually found within rain naturally. Have you ever noticed how your plants seem to react better to rainwater rather than some from the tap? By soaking your plants in hydrogen peroxide solution, it actually replicates this natural substance found in raindrops and your plants drink it up, thinking that it’s ordinary rain!
How To Use Hydrogen Peroxide
Using hydrogen peroxide for gardening is pretty simple, but getting the mixture right is key. You want to soak your plants, around the roots, and get rid of fungus, spores and built up mold.
A general rule of thumb is to mix about one cup of HP solution with 32 cups of water and head out into the garden in the evening. Pour the solution into your pots or flower beds and leave it to soak overnight. Make sure you concentrate on the roots of your plant and avoid spraying the solution onto flowers or leaves.
You can also use a stronger solution to help seeds. One ounce of it as a solution in two cups of water will give you a great solution for seeds. This helps them stay healthy and grow faster.
1. Soil Aeration and Treatment of Root Rot
Good soil aeration is really important for any garden plants. Giving your soil enough space for air and nutrients to get through to the roots of your plants is the best way to see your plants flourish. If your soil is too compact, oxygen and nutrients won’t get through and your plants could die. A good way to see if your soil is too compact is to look at the roots of plants you have growing currently. If you pull out a plant and the roots look all squished together and tangled up then it means the soil doesn’t have enough aeration and your plant is struggling. You will also see more toxins and disease in your soil if it is poorly aerated.
Root rot is another problem that can crop up if your soil is too compact. Typically seen in plants which have been overwatered, it is the most common cause of decay around roots of plants and shrubs. Known as Phytophthora root rot, it doesn’t just affect plants in containers as bedding plants and bulbs can also suffer from this.
The difficult thing with root rot is that it can sit for years in your soil even if it hasn’t had any plants put in. It is difficult to treat because of this and is exacerbated when the ground is waterlogged or very compact. The most common time gardeners will see root rot is in potato and tomato gardens.
The signs you have root rot in a plant can be difficult to spot as it doesn’t appear above ground until it has well and truly taken over your plant. You will see yellow leaves and some branches dying off completely. If you dig around the roots of the plant you will see the roots are not formed well enough.
The good news is it can be treated with hydrogen peroxide. So, if you discover root rot or believe your soil is badly aerated, here is what you can do. It can and will kill off bacteria and fungus.
Use a weak solution (around 3%) and mix it roughly one part chemical to two parts water. Carefully pour it around the roots and the base of your plant to kill off the bacteria.
2. Disinfect Growing Medium
There are hundreds of different types of growing media available. Put simply, a growing medium is a solid or liquid compound which is designed to help plants grow. This can be anything from a compost mix to a peat mix. Organic potting compost will have organic matter in it which can include bone meal, worm castings and even bat droppings! While this is great and packed full of nutrients for your garden and containers, you do run the risk of introducing bacteria and fungus into your garden through using this type of potting mix.
An easy way to stop disease infiltrating your garden this way is by disinfecting your chosen growing medium before you use it with a hydrogen peroxide solution.
Just put your chosen soil or potting mix into a clean, disinfected container and then sprinkle over some hydrogen peroxide mixture. The same sort of mix as you would use to pour over a plant suffering root rot. Allow this to settle in over a week or so, watering two or three times and then it should be ready for use in your garden or containers.
3. Sanitize Seeds
Everyone knows that seeds do best if they are soaked in water first, but did you know that using hydrogen peroxide in your water solution will help them germinate faster? Hydrogen peroxide will also kill off any bacteria that your seeds may have picked up. So if you’re buying them from another gardener you can make sure you get the plants you want without bringing in any unwanted diseases into your garden. Use a 3% hydrogen peroxide solution and pour it into a small, watertight container. Leave the seeds for around four hours and this will kill off bacteria without affecting the seeds.
You should then rinse the seeds thoroughly in clean, fresh water and then leave them to dry on a kitchen towel or a clean tea towel.
4. Accelerate Germination
Soaking seeds in hydrogen peroxide can also accelerate germination and even just a minute or two in a weak solution can speed up how fast your seeds will sprout. Put the seeds in a sieve or if you can a mesh bag works best. Something that will allow water through while keeping the seeds in place. Unlike bleach, hydrogen peroxide takes off any bacteria without damaging the seed itself. It should be a solution of one teaspoon in about a cup of water for the seed soak. You can use a much lower concentration but the soaking process will take much longer. You should rinse your seeds with water and then begin the germinating process straight away. You can use a thin layer of wet kitchen towels or sprinkle some potting soil into a seedling tray.
These trays are often made of cardboard or other absorbent material which will keep the seeds moist until they need to sprout. Read your seed instructions carefully and keep them at the right temperature. Warm and moist is best and, generally, seeds thrive in a warmer climate so think about putting them in a seed propagator or greenhouse.
5. Boost Root Development
If your plants are looking a little limp and lifeless, then give them a boost with a dose of hydrogen peroxide. While you can definitely use it as a seed booster and deal with fungal growths, it is also great for helping plants at any stage of their life do better. The hydrogen peroxide solution can be sprayed or absorbed straight into the soil to help boost your plant’s roots.
Watering plants with hydrogen peroxide solution will introduce more oxygen into your soil. This boost of oxygen gives the roots more room to take in extra nutrients and water to feed and it will give it a kick start or help an ailing plant get back on track. Use about two teaspoons of 35% hydrogen peroxide to around one gallon of water and then use it on your garden every other time you go out to water your plants.
6. Fight Fungal Infestions
One of the best uses for hydrogen peroxide is to fight fungal growth or mold on plants. You might be concerned about using something that will kill mold and spores around your precious plants but you don’t need to worry. This chemical mixture is brilliant at killing off fungus while also being kind to your shrubs.
If you spot the tell-tale signs that a fungus has taken hold of your plants, then mix up some hydrogen peroxide solution and water your plant really heavily. And I mean really heavily. You want to almost flood your plant and keep watering until the liquid pours out of the pot or the flowerbed is waterlogged.
Don’t panic! This might sound like bad advice but using this much “clean” water will completely rid the area, and soil around your plant, of the bacteria-carrying dirt and flush it clean. Don’t let your plants sit in a tray of water, though. Water them in one place and then move the container to another. Leave the watering until the plant has very nearly completely dried out and you should see the fungus die off. So, remember; hydrogen peroxide for powdery mildew, residues, and mold is the most effective and safe.
Mixing charts for gardening with hydrogen peroxide
If you want to start gardening with hydrogen peroxide, you need to know how much peroxide to use. Here are charts to tell you how much!
To water or mist plants, to soak seeds, to add to water used to wash sprouts:
| WATER | ADD THIS AMOUNT OF 3% HYDROGEN PEROXIDE | ADD THIS AMOUNT OF 35% HYDROGEN PEROXIDE |
| 1 cup | 1 and 1/2 teaspoons | 7 to 10 drops |
| 1 quart | 2 tablespoons | 1/2 teaspoon |
| 1 gallon | 1/2 cup | 2 teaspoons |
| 5 gallons | 2 and 1/2 cups | 3 tablespoons plus 1 teaspoon |
| 10 gallons | 5 cups | 6 tablespoons plus 2 teaspoons |
| 20 gallons | 10 cups | 3/4 cup plus 1 tablespoon plus 1 teaspoon |
To spray on sick or plants with fungus:
| WATER | ADD THIS AMOUNT OF 3% HYDROGEN PEROXIDE |
–OR– ADD THIS AMOUNT OF 35% HYDROGEN PEROXIDE |
| 1 cup | 1 tablespoon | 1/4 teaspoon |
| 1 pint | 2 tablespoons | 1/2 teaspoon |
| 1 quart | 1/4 cup | 1 teaspoon |
| 1 gallon | 1 cup | 1 tablespoon plus 1 teaspoon |
| 5 gallons | 5 cups | 6 tablespoons plus 2 teaspoons |
| 10 gallons | 10 cups | 3/4 cup plus 1 tablespoons plus 1 teaspoons |
| 20 gallons | 20 cups | 1 and 1/2 cups plus 2 tablespoons plus 2 teaspoons |
Please be mindful to choose the correct column in the chart depending on whether you are using 3% hydrogen peroxide or 35% hydrogen peroxide!!
As you may notice, the amount of peroxide in the chart for sick and fungus infected plants is twice as much as in the first chart. I have heard of people using stronger solutions, but more is NOT always better. So be careful, and when in doubt, stay safe. You can always apply more another day. If you decide to use a bit more, please make it only a bit more, don’t get carried away. Gardening with hydrogen peroxide is great, but too much can harm your plants. 10% hydrogen peroxide is recommended as a weed killer — in other words it will kill your plants at that concentration.