Using activated charcoal for orchid medium - Orchid Board

newflasker · #1 10-25-2007, 10:27 AM

I am testing my home-made orchid medium by adding activated charcoal (AC) for germinating seeds and growing seedling. I don't see any different whether I add AC or not. Even worse, some seedlings grow so slow. Many people said that add 1-2 gram/liter AC will improve root growing but I don't see that way. Anybody has the same problem? What kind of AC are you using and where do you buy it?

Nguyen

Lagoon · #2 10-25-2007, 11:57 AM

Bonjour!

I don't know about the growth thing. But you can get this Active -carbon in any pet shop, it comes in granular and powder forms.

Ross · #3 10-25-2007, 12:17 PM

I use agriculture type charcoal and it works great for Tolumnias (100% large chunk charcoal) I think the problem may be the activated part?

Lagoon · #4 10-25-2007, 12:25 PM

Opps! Misread the the posting. I would think that activated carbon would make it very alkaline.
What are you growing?

newflasker · #5 10-25-2007, 01:49 PM

Quote:

Originally Posted by Lagoon

Opps! Misread the the posting. I would think that activated carbon would make it very alkaline.
What are you growing?

In my medium, I adjust the pH to 5.6 (for seedlings). I am growing Phal. and Den. I will go to the pet shop for AC powder and try. Hope it's better.

FinnBar · #6 10-25-2007, 02:13 PM

i doubt it would rise the alkalinity, more like the opposite. if my memory serves me right AC will adsorb ions from the water which in most cases would be a minus -losing nutrients from fertilizer solution..
as a growing medium i don't think it would be any better than regular charcoal. but my knowledge on the stuff is based on aquariums not orchids though..

Ross · #7 10-25-2007, 02:44 PM

Quote:

Originally Posted by FinnBar

i doubt it would rise the alkalinity, more like the opposite. if my memory serves me right AC will adsorb ions from the water which in most cases would be a minus -losing nutrients from fertilizer solution..
as a growing medium i don't think it would be any better than regular charcoal. but my knowledge on the stuff is based on aquariums not orchids though..

That's sort of what I thought also. I only use ag grade charcoal because it is relatively inert, holds water, and is a minor source of carbon. Beyond that I might as well use marbles. Activated charcoal is primarily used to absorb nutrients and/or gases and may be the problem.

Ross · #8 10-25-2007, 02:51 PM

Here's a reference I found on "How Stuff Works" web site -> "Charcoal is carbon. (See this Question of the Day for details on how charcoal is made.) Activated charcoal is charcoal that has been treated with oxygen to open up millions of tiny pores between the carbon atoms. According to Encylopedia Britannica:

The use of special manufacturing techniques results in highly porous charcoals that have surface areas of 300-2,000 square metres per gram. These so-called active, or activated, charcoals are widely used to adsorb odorous or coloured substances from gases or liquids.
The word adsorb is important here. When a material adsorbs something, it attaches to it by chemical attraction. The huge surface area of activated charcoal gives it countless bonding sites. When certain chemicals pass next to the carbon surface, they attach to the surface and are trapped.

Activated charcoal is good at trapping other carbon-based impurities ("organic" chemicals), as well as things like chlorine. Many other chemicals are not attracted to carbon at all -- sodium, nitrates, etc. -- so they pass right through. This means that an activated charcoal filter will remove certain impurities while ignoring others. It also means that, once all of the bonding sites are filled, an activated charcoal filter stops working. At that point you must replace the filter."

This makes me wonder if the wimpy growth of the seedlings is due to absorbtion of the necessary nutrients by the charcoal?