How to Use Hydrogen Peroxide for Plants (Hint: Experts Say in Moderation)

How to Use Hydrogen Peroxide for Plants (Hint: Experts Say in Moderation)

Although there are many articles about hydrogen peroxide for plants, it actually has few proven uses related to gardening. As Jeff Gilman, Ph.D., author of… The truth about garden remedies “In my testing and limited experience, it has no benefit at all in disease control,” points out the director of the University of North Carolina Charlotte Botanical Gardens.

Hydrogen peroxide “is a surface sterilant, and for that purpose it works well,” Gilman says. But it degrades quickly when applied, so it will not provide permanent disease control. It’s just water with an extra oxygen atom in it, so it’s useless as a fertilizer and not something you can rely on for pest control.

Benefits of using hydrogen Peroxide for plants

Since this chemical compound kills good microbes as well as bad ones, you may want to avoid using it on soil in most cases. So, in terms of secret gardening ingredients, peroxide for plants might seem like a pretty big fail! But household staples have a few uses for home gardeners.

Disinfects surfaces of tools and products.

As Gilman notes, peroxide is a surface sterilant. The same qualities that enable it to clean cuts and scrapes also enable it to clean bacteria and fungi from the blades of gardening tools, as well as planting trays. It can even clean the exterior surfaces of the product. However, keep in mind that a University of California study found that peroxide did not kill fire blight bacteria as much as other disinfectants (such as bleach, pine sol, and Lysol).

Promotes seed germination by eliminating fungi.

A North Carolina State University study conducted by Robert M. Jetton and W. Andrew Whittier determined that Atlantic white rice seeds soaked in hydrogen peroxide for one hour before planting germinated at a much higher rate than unsoaked seeds or soaked in other sterilizing solutions. “Soaking seeds in hydrogen peroxide is known to be effective in sterilizing seed coats infected with pathogenic fungi,” the study authors stated. Naturally, it is the seed types that are most frequently infected by the fungus that require such a “bath”.

Cleans the surface of the seed mixture.

If white mold appears on top of the seed starting mixture during the seed starting process, you can spray the surface with a water/peroxide solution to eliminate the mysterious intruder. Also, if your seedlings are starting to die back due to damping off disease, you may want to mist their soil mix with a diluted hydrogen peroxide plant spray. This can help contain the carnage by controlling the fungi causing it. Seed starting mixes are often sterilized anyway; If so, you may not be killing any good bacteria in the process.

It adds oxygen to oversaturated soil.

Although hydrogen peroxide does not add any nutrients to the soil, making it useless for typical fertilization, it is sometimes used in oxygen fertilization. A University of Florida article notes that the result of drenching plants with salt water is often “the air in the soil being replaced by salt water.” As a result, not enough oxygen reaches the plant roots, and the plant cannot support “root aerobic respiration.” The researchers indicate that adding a small amount of hydrogen peroxide when watering these plants may be enough to save them.

Photo: istockphoto.com

Apply hydrogen peroxide to the soil

To mix a hydrogen peroxide solution for plants prone to damping off, mix 1 tablespoon of hydrogen peroxide with 1 quart of water. (Use typical 3% drugstore hydrogen peroxide in your garden.) To combat mold, mix 4 tablespoons of peroxide per pint of water.

When watering plants with hydrogen peroxide, either spray the surface of the seed mix with your solution or water the container from the bottom with this solution until the surface is wet. Just keep in mind that the effects of peroxide do not last long. Therefore, for seedlings that are particularly susceptible to damping off, you may need to apply new treatments on a regular basis.

To add oxygen to hypoxic soil, the University of Florida recommends using just one teaspoon of peroxide per gallon of water when watering affected plants.

Avoid spraying hydrogen peroxide on foliage and roots

As for applying hydrogen peroxide to plants, it is best to avoid it. As Nick Goltz, director of the Plant Diagnostics Laboratory at the University of Connecticut, notes, “Hydrogen peroxide sterilizes surfaces and can reduce bacteria and some fungi. But the rapid reaction that gives hydrogen peroxide its sterilizing properties occurs almost immediately after it comes into contact with other compounds. This does not allow the hydrogen peroxide to move Throughout the plant.

This means that its use will not affect most pathogens (disease-causing organisms) if the fungi or bacteria are present in the tissues of the plant and not on its outer surface. “Excessive or incorrect use of hydrogen peroxide can exacerbate plant health problems by drying out surfaces and killing beneficial microbes,” says Goltz.

You’ll also want to avoid using undiluted hydrogen peroxide for root rot, as is sometimes recommended. A study on moth orchids demonstrated that even 3 minutes of exposure to this compound could damage the roots, and peroxide did little to subdue algae clusters around the roots.

A person cleans pruning shears with hydrogen peroxide.
Photo: istockphoto.com

To disinfect garden tools and supplies such as pruning shears and flatbeds, soak them in a solution of 1 part 3 percent hydrogen peroxide to 4 parts water. For cleaning products, Seattle Times columnist Teresa Graydon recommends using a 3 percent form of food-grade peroxide rather than the typical drugstore product. Add only about ¼ to ½ cup of it to a gallon of water, and soak the product for 10 to 20 minutes, making sure to rinse it with clean water afterward.
Although drugstore hydrogen peroxide should work well enough for amateur gardeners, there are stronger types of hydrogen peroxide available for professional growers. In those cases, peroxide is often mixed with other ingredients and is used primarily for greenhouse sanitation.

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