How to Use Hydrogen Peroxide for Houseplants (Step-by-Step)

In a perfect world, houseplants need little maintenance, survive all of our neglect, and still somehow look luscious and amazing. But that’s just not the case. Without proper upkeep and attention, houseplants can end up looking- and feeling- pretty sad.

One of the most overlooked aspects of keeping houseplants is keeping them free of pests, disease, and other infections. In fact, some of the most widespread plant illnesses can be easily prevented with simple treatments involving everyday household materials.

Uses of Hydrogen Peroxide for Houseplants

When it comes to the longevity of your plants, hydrogen peroxide is here to help. In fact, incorporating hydrogen peroxide into your regular houseplants care routine can save you tons of time (and plants) down the road. Always remember to dilture your hydrogen peroxide to 30% volume in water before using it on plants. Here are a few ways to make use of hydrogen peroxide.

Treat Root Rot

The most detrimental and hard to spot ailment in plants is root rot, which can be tricky to detect until it’s (almost) too late. Root rot happens for a couple of reasons, namely those related to watering.

Overwatering is the leading cause of root rot in houseplants, and it will affect every plant in your space eventually, whether you notice it or not. Plant roots are especially susceptible to rot if they’re overwatered, even once. You can prevent overwatering by ensuring that your plants have proper drainage in their pots so that water never sits at the bottom.

However, watering too often even with proper drainage can rot your plant’s roots. When they’re constantly exposed to dense, heavy, saturated soil, they ca’nt absorb oxygen; then, the outer layer of the root dies, leaving the sensitive inner tissue exposed. This tissue can then be exposed to pathogens like bacteria and fungi that naturally occur in soil, but are usually kept at bay by the root’s outermost protective laters.

The same can happen with underwatering. If a plant goes unwatered for too long, the roots will die; then, once they’re resaturated by water, the dead tissue absorbs the water and becomes the perfect meal for all sorts of common plant pathogens. These two issues lead to the same fate: root rot. Once it sets in, it needs to be treated right away.

Here’s how to treat root rot with hydrogen peroxide:

1. Unpot the plant. Remove every trace of soil from the roots and discard it; then, rinse the roots out until there’s no visible soil remaining. Make sure to gently untangle the roots to get between them at the base.
2. Remove the affected roots. Using sharp, sterile shears, entirely remove any roots that are dark in color, mushy, or emit a pungent odor. Healthy roots will be white or very lightly colored for most houseplants, so be sure to leave those.
3. Prepare a hydrogen peroxide mixture. It’s important to dilute the hydrogen peroxide before applying it to the roots. Using a 3% hydrogen peroxide (drugstore grade), mix one part hydrogen peroxide and two parts water into a bowl or spray bottle.
4. Treat the remaining roots. Use this mixture to either mist or briefly submerge the plant’s roots, coating them evenly. This will help to prevent the spread of any pathogens in the root system, and will discourage excess pathogen growth around the roots as they settle into their new soil.
5. Repot the plant. From here, you can then repot your plant into a container that has plenty of drainage. Use fresh soil to avoid recontamination, and water in thoroughly. Be sure to monitor the soil conditions.

Of course, there’s always other methods of contamination to worry about. Fungus gnats, which are tiny flying insects that often take over houseplants, are not only harmful themselves but can also act as a vector to transmit pathogens from one plant to another. The spores simply spread by latching onto the feet of these little pests, hitting soil when the gnats touch down to burrow.

Fungus gnats can also be treated and kept at bay using hydrogen peroxide. The acidic nature of the chemical makes houseplant soil uninhabitable for them, and without any food from inside the soil, they quickly die.

Here’s how to use hydrogen peroxide to eliminate fungus gnats:

1. Find and isolate affected plants. When you first notice fungus gnats in your house, they’ve likely already been there well over a month. The average lifespan of a fungus gnat is about four weeks, so if you’re just now seeing them, check your other plants. If they remain unaffected, try to move the affected plants away from them, such as in another room with a door that closes.
2. Prepare a hydroge peroxide mixture. Using a watering can or measuring cup, combine one part 3% hydrogen peroxide with two parts water. Mix to dissolve the hydrogen peroxide in the water.
3. Apply the mixture to the soil. To better distribute the mixture throughout the soil, use a skewer to poke a few holes into the soil; this will both aerate the soil and allow the mixture to seep into some hydrophobic areas, such as the edges. Then, water the plant very thoroughly with the mixture until it has all drained out the bottom of the pot.
4. Repeat. Since it takes around a week for an egg to develop into a hungry larvae, you should treat the soil every five to seven days until the gnats are gone and you don’t see any flying around nearby. This entire process could take about a month, but it’s well worth it to eliminate these pests.

It’s also a good idea to automatically treat every plant that you bring home the same way; if it doesn’t need to be immediately repotted, you can simply treat once a week for the first month to make sure there aren’t any fungus gnats waiting to hatch in the soil.

Using Hydrogen Peroxide Above the Soil

Hydrogen peroxide can also be used to deal with pests, including spider mites, powdery mildew, and even some types of mealybugs in conjunction with other treatments. These issues may take some time to notice, which gives the infestation a chance to get into the tiny cracks and crevices of your plants.

Here’s how you can eliminate pests and diseases using hydrogen peroxide:

1. Remove as much of the infestation as possible. If you end up with mealybugs like scale, spider mites, or even powdery mildew, use a damp cloth to remove as much of the physical problem as possible. Scale insects may require rubbing alcohol to remove effectively, but use with caution, as the gasses of this chemical can be toxic.
2. Prepare a hydrogen peroxide mixture. For most infestations, you can turn up the heat on your hydrogen peroxide mixture if it’s used above the soil and not within the roots. Mix a 50/50 ratio of 3% hydrogen peroxide with water in a spray bottle and gently shake to combine.
3. Isolate the affected plants. Pests and diseases can spread quickly within a plant and to your other plants, so make sure to move affected plants away from healthy ones and check them frequently, as well. Try not to allow affected plants to hang over unaffected ones.
4. Spray the affected plants well. Now that the affected plants won’t be spreading their illnesses to other plants, you can treat them. In a sink, tub, or bin, spray down your plant in every place possible, focusing on the undersides of leaves, any place where a stem intersects, and where two leaves or stems may be touching. These are high-risk areas where pests often hide.
5. Continue treatment until the problem is gone. This treatment can be used twice per week on an average tropical houseplant and most succulents, so consistency is key. Be sure to spray your plant every couple of days to make sure there are no eggs or spores that have survived the first treatments. Once the plant shows signs of recovery, such a new growth or dropping affected leaves, stop the treatments but continue to monitor the plant closely to make sure no other unwanted guests spring up again.