How to Use Hydrogen Peroxide On Houseplants

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Hydrogen peroxide was one of those ‘scary products that I avoided until, er, this year, because I didn’t want to burn myself/burn my house down/give myself a terrible dye job.

It’s super handy to have around though. I don’t use it often (I think my boyfriend uses it more than me for mysterious aquarium-related purposes)but it’s one of those things that’s good to have on hand, like surgical spirit/rubbing alcohol or a spare pot.

Maybe you’ll never need it, but you can guarantee that if you don’t have it, you’ll need it.

What is hydrogen peroxide?

Hydrogen peroxide is a reactive oxygen species (who knew we called such things ‘species?’). The formula is h2o2, which just goes to show how important a single oxygen can be, because water it ain’t.

In its pure form hydrogen peroxide is a light blue liquid that’s a bit more viscous than water. It decomposes when exposed to light, which is why all the stuff I’ve bought comes in a cardboard casing.

Hydrogen peroxide is primarily produced for its bleaching properties. Hair dye is an obvious one, but foodstuffs like flour are often whitened with hydrogen peroxide.

It can also be used as a mild disinfectant and as an explosive. You can’t say it doesn’t have range.

Does hydrogen peroxide kill root rot?

I do have articles on root rot, but let me direct any newbies to this video on root rot, since I can cover a lot more in a video than I can on paper.

Hydrogen peroxide can’t reverse root rot. Once a root is rotten, as far I’m aware, there’s nothing you can do to bring it back, BUT you can use hydrogen peroxide on your plant’s roots to kill the bacteria that’s causing the root rot.

It also adds oxygen back into the soil.

In my experience, it works really well but you do need to ensure that you’ve identified the origin of the root rot bacteria.

It’s usually caused by a lack of oxygen in the soil/water/whatever medium that you’re growing your plant in, so be sure that you don’t make the same mistake again. Whilst hydrogen peroxide can be a great cure for root rot, prevention is better than cure.

Can I soak my plant in hydrogen peroxide?

I mean technically, you could, and it can be tempting when plants are infested with pests, but I prefer to water mine into the soil, and if I’m using it on the leaves I’ll apply it with a spray bottle.

Hydrogen peroxide is, in general, safe to use on plants, but I still think it’s worth exercising caution, especially if you’re new to using it or you’re using it on a valuable plant.

How do you use hydrogen peroxide on plants?

As I said, hydrogen peroxide can be used on house plants perfectly safely, but you do need to dilute it. It is, after all, capable of turning hair yellow (or green, in some exciting cases) and bleaching flour, so we need to dilute it.

I use 3% hydrogen peroxide. I have no idea what the other 97% consists of, I assume regular old h2o. Even at only 3% strength, you have to dilute it further.

What is the ratio of hydrogen peroxide to water for plants?

For pest care: one teaspoon of hydrogen peroxide per cup (240ml) of water. I use a measuring jug for water, and usually do one teaspoon per half a pint of water (250ml) because, er, those are the measurements I have on the side.

For treating root rot: increase from one teaspoon to one tablespoon of 3% hydrogen peroxide in the same volume of water.

If you use a higher concentration of hydrogen peroxide on the foliage of the plant you run the risk of burning it. You could burn the roots, but since it’s necessary to kill the root rot-causing bacteria, it’s a risk worth taking.

I just use regular tap water, rather than distilled or filtered, in case anyone was wondering.

How often can you use hydrogen peroxide on plants?

I would only use it as often as is necessary, but wouldn’t recommend using it more than twice a week.

If I’m treating a plant for pests or root rot, I’ll either spray the leaves or the soil with a hydrogen peroxide solution once a week until the issue has been resolved.

Will hydrogen peroxide kill bugs in soil?

Yes, if used consistently. I have an article on my preferred method of getting rid of pests here, that highlights how consistency is the most important part of getting rid of pests on house plants.

Hydrogen peroxide can be used to get rid of all kinds of pests, including thrips, but it isn’t any more effective than other methods, and success rates will depend a lot of the level of infestation, the health of the plant, and the tenacity of the pests.

I used hydrogen peroxide to get aphids of my rabbit’s foot fern, but it didn’t work on my Philodendron tortum. I have no idea why!

Is hydrogen peroxide bad for the soil?

I don’t want to put anyone off using hydrogen peroxide, but I don’t you to be using it as a cure-all for all your plant woes too.

Unfortunately, hydrogen peroxide can’t differentiate between pests and beneficial microbes in the soil, so if you use it a lot, you may find that your plants start to suffer, especially if you’re not the best at remembering to fertilise your plants consistently.

How do you use hydrogen peroxide as an insecticide?

You can either use it as a foliar spray (using the ratio detailed above) or by watering it into the roots. I would use one teaspoon per 250ml of water to reduce the chance of it damaging the leaves of your plant.

From what I’ve read, hydrogen peroxide kills pests (especially the larvae) on contact, so if you’re worried you’ve used too much hydrogen peroxide, you should be able to rinse your plant off afterwards without undoing the work of the hydrogen peroxide.

If you have a bad infestation, then spray your plants a couple of times a week, gradually decreasing over time until you’re confident the pests are eradicated.

Does hydrogen peroxide kill mould and fungus?

Yes, and I would use it in the same way as you would for an insecticide.

It’s not necessary to use it to kill off those little mushrooms that you sometimes find growing in houseplants (read all about mushrooms in house plants here), but if you have any black spots that you think might be fungus, then a hydrogen peroxide foliar spray can help to get rid of that.

I just use this hydrogen peroxide from Amazon. I’m pretty sure that one brand is much like another, but make sure to check the strength – you don’t want to be merrily applying 30% strength hydrogen peroxide by accident!

Caroline Cocker

Caroline is the founder and writer (and plant keeper) of Planet Houseplant

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