Charcoal removes impurities from the water (including fertilizer). There have been endless discussions as to it's benefits. I never use it.

nick

I don't know of any proven benefit to using carbon in potting media. Many people claim that carbon removes "impurities" because of carbon's use in filtration, but there are too many unknowns to make that conclusion based on this fact alone. When used for filtration, carbon typically has air or water actively circulated through it, but in potting media it plays a passive role. Carbon also has a finite lifespan; it eventually fills up and becomes exhausted. We have no idea if this lifespan is 2 weeks or 2 years when used in potting media. And then there is the question of whether the substances adsorbed by carbon are beneficial, detrimental, or inconsequential. My guess is that carbon's only real benefit is the psychological assurance it provides to those that believe in its value.

That said, I doubt that carbon would adsorb any significant fertilizer salts. Carbon is best at adsorbing large organic molecules. The ions in synthetic fertilizers would be too small to be adsorbed by carbon. For example, carbon is used to remove organics in saltwater aquariums which have much higher concentrations of ions like sodium, chloride, calcium, magnesium, sulfate, etc than any organics. And yet the carbon removes organics without becoming clogged by the seawater itself.

I would skip carbon unless you like its other properties like water retention, cost, durability, etc. I wouldn't know because I've never seen any reason to use it.

-Chris

Orchid roots seem to love it. I use it when I run out of large bark. Roots always seem to attach to the chunks.

Jane

Charcoal has proven benefits for a wide range of pot plants. Its chief plus is that it soaks up a lot of impurities, including bacteria and fungus from the compost. If you use an organic compound such as bark, which decomposes relatively rapidly, as a basic compost you're almost obliged to add a little charcoal. I don't use it because I use mainly tree fern and/or sphagnum moss which have similar properties, but I know it is highly recommended. Good luck. - Ian.

"Charcoal has proven benefits for a wide range of pot plants. Its chief plus is that it soaks up a lot of impurities, including bacteria and fungus from the compost. If you use an organic compound such as bark, which decomposes relatively rapidly, as a basic compost you're almost obliged to add a little charcoal."

Fungi and bacteria should not be a problem in proper potting media. I use bark (which is popular because of its slow rate of decomposition with respect to other organics) in many of my mixes and have never had an issue with it. But if there were an issue, charcoal would not help. Fungi and bacteria actively grow and adhere to their food sources. These mycelia and bacterial films can't be adsorbed by charcoal.

The vague "impurities" that people talk about are not a problem if one uses proper potting media, water sources, and fertilizers. In the unlikely event there is a toxin in your growing scheme, you need to eliminate the source of the problem by changing one of the above factors. Charcoal is a band-aid solution, and most likely a completely ineffective one at that.

-Chris

Charcoal has been used for years and years in orchid media. I don't have a clue if it absorbs anything or not but the one thing it will do is keep the media open with an inert material that won't break down. Orchid growers in areas where the heat and humidity are constant will many times use only charcoal in a pot.

Brooke

Hi
One unmentioned plus to charcoal particularly for vandaceous orchid is the rampant roots tend to cling to it
helping to keep them contained. I use no media at all on the family and mostly crushed lava rock for Phals Catts Brassidium . because I keep them out doors. gary

I've used charcoal in my orchid mix for years and years. Is it better than just straight bark and perlite? The medium does seem to be more airy and hold up longer under my conditions if there is charcoal in it; it doesn't compact so quickly and turn to brown sludge.

In my local society, one of our Mississippi growers uses straight medium-grade charcoal to grow many of his plants in -- and they are stunning!

Interesting, I know active carbon removes media from water until it fills up, I wasn't aware of the orchid applications.
So where do you get it?
I looked at the Siemens website, they must have 40 different types of carbon, head began to hurt. Never knew that there were sooooo many different varieties. In case anyone wants to feel my pain...
http://www.water.siemens.com/en/products/activated_carbon/granular_activated_carbon_gac/Pages/default.aspx?stc=wwiis250026