Question
Hi. I'm a student. My gardening teacher told us about the medium used for potting and she gave us a question:
Why do people use charcoal to plant orchids and what is contained in charcoal?
I have no idea what this means, because I never planted an orchid before! So please give me some help on the followwing:
1. Is it true that charcoal is used to plant orchids?
2. If it is true, why?
3. What is conained in the charcoal (i.e. which types of minerals)
Thanks!

Answer
Charcoal is often used as an ingredient in an orchid potting mix because it is inert (will not decay), allows the flow of air thrugh the potting mix, and, some believe, it binds certain toxins from the metabolism (breakdown) of the organic components of the potting mix.  Charcoal is carbon resulting from the burning of wood. I should point out that some experienced growers often grow orchids without the use of charcoal so it is not aan essential ingedient.  There is growing resistance to using charcoal in orchid potting mixes because large areas of rainforest are destroyed to produce charcoal by the burning of the rainforest trees

Most commonly, charcoal is only one ingredient in a potting mix and rarely is it used as the only ingredient.  Most potting mixes have both organic and inorganic components.  These are needed in the proper balance to help keep moisture at the roots, provide some nutrition, permit air movement through the mix, and help to firmly anchor the plant in its pot.  Organic ingredients in the mix may include sphagnum and/or peat moss, fir bark and osmunda fiber.  Inorganic ingredients include perlite and lava rock.