Years ago, charcoal was suggested as a way to "keep potted soil sweet". Is this practice still in use today? Could it give a plant an extra year or two in a pot (assuming it wasn't rootbound yet)?
Charcoal works by absorbing and binding volatile substances (including substances which have unpleasant smells). So all it does is stop soil getting to smell nasty. It doesn't do anything to provide extra nutrition for the plant.
I don't know why it is used in orchid mix, but it is commonly used in terrariums it stop them smelling.
Our woodstove burns seasoned apple wood. Quite a few chunks left when cleaned out. Ashes are scattered thinly around clematis. Wondered if charcoal could be used when repotting houseplants. Is it the salt/fertilizer accumulation that smells nasty? Could charcoal prevent fungus?
The horticultural charcoal is "activated charcoal" and differs from normal home burnt wood coal. The bad smell is rotting material that produces things like amonia and other nasty stuff. No, it shouldn't have any impact of fungus gnats. If you've got gnats you water too much, that's all.
So activated charcoal refers to "large surface area", i.e. charcoal for water purification. I had always wondered what activated meant. Informative link, thank you.
The use of biochar is discussed with enthusiasm by many in the green movement. There is a great deal of research and real time experimentation using charcoal. Googling terra preta or eprida shows links to interesting work on the effectiveness of biochar. The info that i reviewed piqued my interest enough to go ahead and test it out on some slower growing potted trees. I'll post the outcome in time. http://en.wikipedia.org/wiki/Biochar
Charcoal has been used in English and Japanese (And medieval Amazonian Indian- who are mostly now dead-thanks Isabella!) horticulture for eons. The art still hangs on in UK where old forests are still sustainably coppiced for charcoal and charcoal is made in the tradition way. In Japan it is an art form. (look at a bonsai potting mix). Unfortunately i have found it difficult to access Japanese research on charcoal on the web. See here fro a few links on the topic:- http://hypography.com/forums/terra-preta/16076-charcoal-in-horticulture.html
