Hydrogen peroxide (H2O2) is a simple product most people have in their medicine cabinet. It’s an inexpensive, effective sanitizer for cuts, scrapes and more. It’s also a great thing to have in your garden shed for root rot!
5 Things Hydrogen Peroxide Can Do For Plants
You may be surprised to learn that H2O2 is an effective substance to use against:
#1 – Fungal infection of potted plant roots (e.g. root rot)
Mix two tablespoons of H2O2 per one quart of water to create a soil drench for plants suffering from root rot.
- To treat root rot, begin by withholding water
- Moving the plant to a well-ventilated area
- Allow the soil surrounding the plant to dry out.
- It should not feel damp when you poke your finger into it.
- Use your H2O2 mixture and water the soil thoroughly
- It should feel damp, but it should not feel soaked
- The goal is for the H2O2 to aerate and disinfect the soil.
- Return the plant to a well-ventilated area
- Wait until the soil has dried almost completely
Repeat the treatment as many times as necessary to eradicate the root rot.
When the plant seems to have recovered, repot using fresh potting soil.
Trim away damaged parts of the plant and its roots. Use a brand new or completely sterilized container.
#2 – Fungal, bacterial and viral contamination of seeds
- Mix one teaspoonful of H2O2 per one cup of water
- Soak seeds for 24 hours before planting
- Soaking accelerates germination
#3 – Fungal and bacterial infection on fruit trees
For small applications, use straight 3% hydrogen peroxide to address fungal growth on the leaves, stems and fruit of fruit trees.
- Apply this using a spray bottle.
- If you have a lot of trees to treat
- Use one-part 35% H2O2 to ten parts water
- Mix up a large batch of spray to apply with a pump sprayer.
#4 – Fungus on plant, shrub and tree leaves
For powdery mildew and/or sooty mold on plant, shrub and tree leaves, mix up a solution of two tablespoons of H2O2 per quart of water.
- Spray the plants liberally, daily until the problem is resolved.
- For large numbers of plants, use one-part 35% H2O2 to ten parts water applied with a pump sprayer.
#5 – Pest infestation
Make a spray to help control a wide variety of common, soft bodied pests by attacking the pests and giving your plants a boost of oxygen.
- Spray heavily initially.
- Examine the plant daily
- Spray as needed to eradicate aphids, mites and thrips.
Hydrogen peroxide is “approved for controlling microbial pests on crops growing indoors and outdoors, and on certain crops after harvest.” [source]
What Strength Hydrogen Peroxide is Best for Garden Use?
For general garden use, the 3% solution you can pick up at any drug or dollar store is fine.
If you have a big job at hand, such as treating a lawn or a damaged tree, look for the 35% solution. You can find in garden centers, feed stores and cleaning supply websites and stores.
This solution is very concentrated, so it takes less to make a great deal of effective H2O2 solution.
For example, with a 35% solution, you could make an H2O2 mixture to treat your lawn or garden for root rot. Mix up 1.5 cups of H2O2 with a gallon of water. Apply using a sprayer or a watering can.
When treating a large area with this strength solution, be sure to apply the mixture at the base of the plants to saturate the soil. Avoid allowing it to touch the leaves. Also be careful not to let 35% H2O2 come in contact with your skin.
It’s best to mix only as much solution as you need at a given time, but it is possible to store leftovers for short periods.
Make sure you keep the solution in a cool, dark place. The refrigerator is ideal. Allow the solution to return to room temperature before use.
Should Hydrogen Peroxide Be Used Preventatively?
Some gardeners think of H2O2 as a fertilizer and add it to foliar sprays and soil drenches on an ongoing basis.
It is important to understand that this chemical is not a fertilizer. It does not provide nutrients, it makes them more readily available to plants.
It does this by delivering a dose of extra oxygen wherever applied. These are the bubbles you see when you clean a cut with peroxide or pour it over plant roots being attacked by fungus or bacteria.
Keep in mind, those bubbles don’t attack harmful pathogens. They also attack beneficial organisms, so regular, ongoing use is not a good idea.
H2O2 is made up of two hydrogen molecules and two oxygen molecules. Water (H2O) is made up of two hydrogen molecules and one oxygen molecule.
Peroxide’s extra oxygen molecule helps plant roots absorb nutrients faster while discouraging the growth of fungus and bacteria.
For this reason, it can be a good occasional tonic, but it’s better to think of it as a medicine than a source of nourishment. Give it to your plants when they are sick and withhold it when they are well.
Will Using H2O2 Regularly Hurt My Plants?
If you dilute your H2O2 correctly and use it judiciously, it can be very helpful to ailing plants. If you overdo your application and/or mix up a solution that is too strong, you can burn or even kill your plants.
As with all garden care products, it’s important to pay close attention to measurements. Act judiciously when applying treatments.
Always test spray a small, inconspicuous area and wait 24 hours before spraying the whole plant.
If the sprayed area shows any sensitivity to your H2O2 solution, you should not use the product on that plant.