Hydrogen peroxide-H2O2

[Ravi]

HP is an unstable liquid it dissociates in to nascent oxygen and free radicals which are responsible in damaging the DNA of a microorganism, in the context of Orchids this makes sense in sanitising root system after they are rid off dead mushy damaged roots.
In clinical practice H2O2 is one of the best time honoured agents in cleansing infected wounds especially gangrenous wounds which are needed to be irrigated thoroughly freeing the wound from sloughing, this exercise is similar to sanitising the dead roots of Orchids.

[Orchid Whisperer]

Don't use peroxide on roots. It will damage or kill them.

[aliceinwl]

I think the problem with using it on roots is that it damages live ones. Roots have permeable tissues and form relationships with mycorrhizal fungi to take up water and nutrients. Blitzing these delicate tissues and necessary fungi with hydrogen peroxide is not good. I could see surgical application to a necrotic area potentially being okay (I've used it successfully to treat early stage leaf and crown rots), but drenching a root system isn't good.

I think application to dead roots is a waste too. Yes, they can be temporarily sanitized but they'll still be dead and will be recolonized by bacteria and fungi that break down dead tissues in short order. I think cutting off dead roots is the better route.

---------- Post added at 11:14 PM ---------- Previous post was at 10:38 PM ----------

I want to add that when using peroxide to treat crown and leaf rots I've paired it with cinnamon powder. I don't know how good cinnamon is as an antibacterial or antifungal agent, but it does seem to be a good desiccant. The cinnamon rapidly dries out the infected area making it less susceptible to further decay. Note the end result is dry dead tissue: not something one would want to subject roots to.

[Ravi]

The label says 3% H2O2 plantgrade, which means it has been brought down from 35% to 3%. My understanding is H2O2 at higher concentrations emits effervescence on application whereas down the low concentrations nothing discernible , will it still cause damage if appled to incised ends of the devitalised roots?

[Orchid Whisperer]

There is no benefit, at all, to putting H2O2 on live roots, cut or otherwise. Putting it on live tissue will create dead tissue (food for fungi, etc.).

Plants have natural mechanisms to cope with cuts, etc. Let the tissue dry, it will heal over, problem solved.

[Ray]

Alan Koch, owner of Gold Country Orchids, pours hydrogen peroxide through his pots as a way to oxygenate the medium.

I haven't used it much, but I've never seen damage from doing so. Frankly, I've not seen much benefit, either.

[Orchid Whisperer]

Originally Posted by Ray

Alan Koch, owner of Gold Country Orchids, pours hydrogen peroxide through his pots as a way to oxygenate the medium. <Snip>

Ray, I'm sure you know that despite what Alan Koch is doing with peroxide, it isn't doing what he thinks it is doing.

Like chlorine bleach, hydrogen peroxide is an oxidizer (oxidizing agent). Stated in simple chemical tems, an oxidizer causes materials to lose electrons. Other oxidizers include fluorine, chlorine, nitric acid, sulfuric acid.

Although the fizzing that happens when peroxide reacts with organic matter is caused by oxygen gas production, that is insignificant compared to oxygen in the medium due to regular air movement through a pot of orchid medium.

Best case scenario, hydrogen peroxide is probably breaking down the orchid medium faster, with some hydrogen peroxide absorbed into root velamen (designed to quickly soak in liquids), where it can break down living tissue.

An oxidizer does not oxygenate. If you want to oxygenate medium, get more air to flow through the medium.

[TomThumb]

I think that the prevalence of people using hydrogen peroxide on roots is due to a very popular youtuber who is also responsible for the popularity of semi-hydro. I admit i did enjoy her videos quite a bit when i first started the hobby and i still watch new ones but my methods differ from hers and i haven't used hydrogen peroxide on roots. I have used it in conjunction with cinnamon to treat crown rot with some success as well as one failure. Her reason for using it is simply because she doesn't like to use chemical forms of pest control. However she sees no issue experimenting with plant hormones to grow keikis so who knows where she wants to draw the line. I will say she often voices the caveat that what works for her may not work for others but her popularity and her vast amount of orchids lead many to follow some of her good advice and some of her bad advice.

[Ray]

OW - I am going to disagree with you on this one - surprise, huh?

Drug store grade hydrogen peroxide is not a very good oxidizer, but when it decomposes - something it does quite readily - it releases oxygen, which seems more like oxygenation than oxidation to me, although I agree whole-heartedly that a good flush with a water breaker probably does as good of-, if not a better job of oxygenation.

[SouthPark]

Originally Posted by Ray

OW - I am going to disagree with you on this one - surprise, huh?

Drug store grade hydrogen peroxide is not a very good oxidizer, but when it decomposes - something it does quite readily - it releases oxygen, which seems more like oxygenation than oxidation to me, although I agree whole-heartedly that a good flush with a water breaker probably does as good of-, if not a better job of oxygenation.

I think so Ray. I can understand relatively high concentration H2O2 doing massive damage. But if low enough concentration, then it's kind of like putting it on our own hand ...... it's not going to destroy the skin, especially when the skin isn't like submerged in the solution for relatively long times.

It might be possible that H2O2 - even diluted - could upset the balance of things - such as kill beneficial organisms already established in or around the root. So wouldn't be surprised if it sets the plant back a bit. On the other hand - I have repotted lots of catts and have sprayed the roots with 6% H2O2 (store-bought bottle from pharmacies, where 6% is kind of typical.... also 3% is available too) ..... which is certainly stronger than 3% obviously. I have not seen any signs of the H2O2 destroying the roots of my plants. My 6% is higher than recommended though --- eg. 3% to 5%. So I'm not recommending people go 6%. I'm just reporting on what I've done many times before.

Whenever I can --- if the roots of my orchids look nice and clean, then I just do my repot with no spraying.