Coconut fiber has been steadily gaining popularity as a growing medium. It comes from the shredded husks of coconuts and can be packaged in a variety of ways. It can be a good substitute for any other type of growing medium since it is now manufactured as pellets, blocks, cubes, and the usual shredded fiber. Coconut fiber is also very commonly found mixed with other media such as perlite or rockwool.
Why use Coconut Fiber as a growing medium?
Coconut fiber is the first totally organic growing medium that works well in hydroponic systems. The fiber is actually a waste product of the coconut industry. It has a larger oxygen capacity and superior water holding ability than rockwool. Coconut fiber is the only growing medium that is naturally high in root stimulating hormones and can help protect against root diseases and fungus infestation. One reason it is so effective is that its purpose in nature is to provide the coconut with a rich medium in which to root when it lands in the soil, so it's just doing what it was designed to do.
Be careful when purchasing coconut fiber that you don't get the lower grade variety. It is not well-suited to gardening due to its fine grained texture and high sea salt content.