Using activated charcoal for orchid medium

[FinnBar]

I just love trying to work out potential growing mediums and their problems..

[Louis_C]

I don't understand the purpose of adding charcoal in flask...Why people add it into their flask? I believe what it dose is to absorb the fertilizer.

[maitaman]

For improved root growth add some vitamin B1 to the mix. Also, phosphorus stimulates roots, but be careful to not overdo. Some mixes are too heavy on nitrogen, which gives faster growth but not any improvement so far as roots go.
Be careful with resinous parts. Pine resin acts as an ion absorber and can remove nutrients, particularly nitrates.

[newflasker]

Originally Posted by Louis_C

I don't understand the purpose of adding charcoal in flask...Why people add it into their flask? I believe what it dose is to absorb the fertilizer.

First, medium darkening improves the root initiation. Add 1-2g/l activated charcoal may helps small seedlings easy get roots. Second, when you transfer seedlings to a new/fresh media you may find the problem which is called phenolic exudation (medium turns brown or black). You also may have this problem when you leave seedlings too long in the flask. When seedlings are stress (because pH is too low in old medium or seedlings get into new medium) they often release phenolic which turns medium brown/black. Third, normal AC absorbs organic compounds and acid but doesn't or little bit absorb mineral salt. Final, many people use AC in medium and found it's good.

[Royal]

Newflasker,

I was going to say the same thing about the darkening of the media. I've read some data that shows this is the only benefit. I dissagree with this statement, and agree with yours -- the absorbsion (or adsorpsion) of phenolic compounds is another plus. For lazy replaters (me), this is a big one.

Do we know for sure that it must be activated carbon? Have you ever just used pulverized hort grade? I understand that there is a difference, but is AC needed for our purposes? Interesting thread.

EDIT: Oh, and I would think that either form of charcoal would be an equal opportunity adsorber.

[Miki]

As you cans see, the question relating to the benefits of adding activated charcoal is debatable. There doesn't seem to be any definitive study that shows any substantial benefit over media not having it. The argument that it adsorbs phenolics has also been disputed, with some saying that such claims cannot be verified. The one thing people seem to agree on is that roots generally grow away from the light, and a dark media encourages root to go into the media. Of course, some others will say that roots photosynthesize to a certain extent so having a darkened media reduces their ability to do so, thus slowing growth. To every argued benefit, there is an argued detriment. The best advice would be to try it (usual concentration is about 2 grams per liter) and see if it works for you. Whatever your results, never mind about what anyone else says. What works for you, works for you, and you should continue doing it (or not, whatever is better).

[Miki]

Forgot to add that in one edition of "Orchid Biology", by Arditti, there was a very specific caution that charcoal must be activated and not just regular charcoal, or carbon black. Adsorbtion is not the same as absorbtion.

[Royal]

Originally Posted by Miki

Whatever your results, never mind about what anyone else says. What works for you, works for you, and you should continue doing it (or not, whatever is better).

Amen to the above! - Royal

Adsorbtion is not the same as absorbtion.

Yes, I wasn't implying that they were the same. Just wanted to be clear I wasn't the expert on the topic. I definitely was not recommending carbon black. They use that to make tires!

Another thought I just had is acidified coconut shell. It has nothing to do with coconut husk or coconut water. It's a natural source of carbon and is used in solvent recovery systems in industrial settings. It is an alternative for carbon beds, recommended for recovery of ketones. It may have similar characteristics.

[newflasker]

Originally Posted by RoyalOrchids

Newflasker,

I was going to say the same thing about the darkening of the media. I've read some data that shows this is the only benefit. I dissagree with this statement, and agree with yours -- the absorbsion (or adsorpsion) of phenolic compounds is another plus. For lazy replaters (me), this is a big one.

Do we know for sure that it must be activated carbon? Have you ever just used pulverized hort grade? I understand that there is a difference, but is AC needed for our purposes? Interesting thread.

EDIT: Oh, and I would think that either form of charcoal would be an equal opportunity adsorber.

Hi RoyalOrchids,
The correct term is adsorption which means binding particles/molecules to the surface but many people use absorption for easy to understand. It doesn't matter as long as we have an idea that some how absorber takes/traps/captures the chemical.

Activate Charcoal (or Carbon) AC is made form charcoal. Charcoal is heat at high temperature to create a porous structure which have extremely large area that can adsorb organic chemical. In tissue culture and orchid propagation, AC is preferred because it's not only darkening the media but it also adsorbs acid (old media get low pH), phenolic and unwanted organic chemical in media. There are many articles about using AC in orchid propagation. I talk to many people who use AC and they like it. However, AC powder is too expensive and not sold for a small quantity (Phytotech only sells 500g or more I believe). One time, I try to grind AC of my water filter (AC of water filter is good): It's too hard and it takes a long long time to get real fine powder so I stop doing it. It's much easy to do it with horticulture charcoal (HC) because it's soft. I tried HC and don't see much different so I ask your guys to see you try it or not. Some people talk about AC in media (not in vitro media) so the question get lost. There no doubt about charcoal in substrate is good but in vitro is good or not? Try it RoyalOrchids and let us know. Cheers

[Royal]

Yeah, I understand the terms. I was referring to "taking away" bad "stuff" from the media. I should have said captures/traps. I also understand that we're talking about axenic culture medium. My point was, that it's role is the same either way. How much does the form matter, if at all?

In potting mix, charcoal prevents the build-up of bad stuff. In replate media, AC prevents the build-up of bad stuff. Both are forms of carbon. I was just raising a question.

Horticulture grade 'charcoal' is carbon. The activation process is a modification, accentuating an existing property of the carbon, whatever the form. Some forms of carbon are better for certain applications. Water treatment plants mainly use anthracite. Industries with air permits use AC or acidified coconut shell. I'm sure there are numerous forms in use to achieve the same end -- adsorbsion. I know how Phytotech is: to purchase all the reagents to make a media for one of my special projects would cost me over $300! It is always good to try cheaper options, especially if you already have them on hand.

I don't purport to know all about AC. It's just I have learned quickly, that there are a lot of myths about tissue culture and asymbiotic germination that have persisted due to blind acceptance.

edit: Man, that sounds too serious. Miki is still right - what works for you, works for you. As long as we share info here, we can avoid re-inventing the wheel. Keep the good info coming!