I've mis-remembered then :(

Yes, my question was rhetorical. There is no one definition of "heavy metal". In fact there are very many definitions of "heavy metal". So to say that "silver is toxic except in minute amounts because it is a heavy metal" is not correct.

My definition of "heavy metal" used to be that it was any metal that accumulated in the body resulting in toxic effects from small amounts. But then I found that people would often reason - heavy metals are toxic, all metals are heavy therefore all metals are toxic. And there are even more definitions. So, I have stopped using the term.

yes, upon investigation I have discovered the term is not a good one - my apologies

I do stand by not recommending it's use other than topically.

While I know that Ray disagrees with using a nine (water ) to one ( bleach ) solution..... I have used this with no harm and great success. I rarely need to do this, but I use this with both black rot & mildew. I mix this solution and let the entire orchid stay in it for up to five minutes. I also use a soft brush to get into the places between the stem & leaf. I then rinse, and let the plant air dry. THIS IS JUST MY OPINION, but it has worked for me for almost forty-five yrs. BettyE

There seems to be a lot of myth floating about. In my case, my Cattleya "Black Caesar" had a severe black rot problem stemming from too much humidity and not enough air. I tried everything including severe pruning coupled with repeated treatments with both Physian and Thiomyl. No luck. New growth came in black. BUT.. after dousing the orchid with Colloidal Silver the Black Rot is now gone. Orchid looks healthy and is growing again. I'm a big believer in Silver. No wonder dentist are now using silver for tooth decay.

The NIOSH guide to chemical hazards indicates that silver is incompatible with, or reactive with, hydrogen peroxide.

Silver does have antibacterial properties, but the U.S. Environmental Protection Agency also considers silver to be potentially hazardous.

Personally, I would avoid the use of such a product in favor of other treatments, if possible.

It works!
 

Despite your best research footnotes, my orchid is thriving BECAUSE Colloidal Silver killed the deadly fungal infection. It works the orchid is thriving. What's wrong with that?

---------- Post added at 12:48 PM ---------- Previous post was at 12:32 PM ----------

I've use h2o2 for fungal problems and it mostly works, but not every time. Colloidal Silver seems to kill fungus dead, without any side effects. My orchids are green and thriving. BTW, There is a new silver based treatment for cavities in people. No more drilling. Silver kills bacterial and fungal problems, I've read the theories, but I'm telling you I've tried it successfully. That's it. Believe it or not.

I have never tried it on my orchids but I take it and I'm still alive. I am a big believer in it. It got me through the weekend a couple of years ago with a tooth infection. I know I would not have made it through without it. By Monday morning the infection was almost gone.

There is a big push by scam artists in the US to take money from people by selling them "colloidal silver" preparations as treatments for all kinds of real and imagined medical problems. Silver does kill a lot of microorganisms on contact, and there are electrolytic systems that use it in place of chlorine to sanitize swimming pools. But silver binds to proteins and other chemicals very quickly, rendering it ineffective in seconds. Use is limited by the tendency of silver to stain things. The black in black and white photography is oxidized silver.

Silver is regarded as a supplement by the US Food and Drug Administration, which means sellers cannot make claims of medical benefit for colloidal silver, nor recommend it for treatment of diseases. As Orchid Whisperer mentioned above, silver catalyzes the conversion of hydrogen peroxide to water plus oxygen gas, so it is not possible to sell hydrogen peroxide mixed with silver in a bottle. Suspension of silver in a colloid does not change basic chemistry. Within seconds it becomes water mixed with silver.

If you search on "colloidal silver" you will find page after page of sites making ludicrous claims of its benefits. Some unfortunate deluded sufferers ingest so much silver their skin starts turning a strange greyish color, called argyrism.

I think it's fine for people here to tell us how they've grown their plants. I don't think most of us want to start seeing long rants trying to sell something.

...and do we even know if a hydrogen peroxide/colloidal silver product will be absorbed and function inside a plant?