Orchid potting mix

Most orchids actually don’t need soil to grow, but rather need an airy mix with really good air flow and drainage. The mixture may consist of: 

Fir Bark, tree Fern, sphagnum Moss, perlite, coco husk chips and/or styrofoam peanuts.

Every mix you find in the stores is unique, and you can even mix your own. Horticulturists from the University of Tennessee recommend the following mix:

orchid bark