Orchid media is readily available and comes in many different forms. They provide root support, root aeration and nutrients. Most of the time several materials are mixed together to create a well-balanced orchid growing mix. To start with, you may want to purchase a ready orchid potting mix from gardening center. With some experience, you will learn that certain material provide air to the roots by opening up the medium. Or you’ll learn some provide more moisture. There is no absolute recipe, because your humidity, watering habit, light intensity and other factors will require different mix. However, each material has its own properties, and you will gain a fundamental knowledge by understanding each of them. Here are some common orchid potting material.
Fir Bark (usually Douglas fir) is a common orchid medium and provides nutrients and root aeration for approximately two years. The finer the particles, the faster the nutrients are released. Fine fir bark is good for seedlings, epiphytes (air plants) and small root orchids, such as the Pleurothallids. Cattleyas prefer medium fir bark.
Sphagnum Moss grows on the top of bogs and can provide nutrients for about two years. It retains 20 times its weight in water and is often wrapped around the roots of orchids mounted on bark. Sphagnum moss also possesses some antiseptic capabilities, can be used alone, and mixed with other media.
Peat Moss holds more water than sphagnum, but deteriorates more quickly. Coarse peat was once a favorite orchid medium, but is now scarce and expensive. Coarse peat moss contains few nutrients, and fine (horticultural) peat is too dense for orchids, but may be mixed with other material to provide moisture.
Charcoal is the result of burned wood, is inert (doesn’t decay) and binds with certain chemicals produced by breakdown of organic material. It’s rarely used on its own, but is a helpful component of other orchid media to provide root aeration .
Coconut Husk Chips are a perfect orchid medium for moisture loving and epiphyte orchids. Coconut husk chips are slow to break down, so last at least two years. The chips must be thoroughly washed to get rid of any salt before being used.
Perlite is volcanic and comprised of silicates. Perlite retains moisture, protects against insects and rot, and provides excellent root aeration. It is rarely used as a sole orchid medium, but is often added to other media.
Vermiculite is a mineral cousin to perlite, with similar aeration characteristics. Vermiculite retains too much moisture to use alone, so is used as an additive in other media, often as a mixture with perlite.
Osmunda is a combination of fern roots. Once a favorite for epiphyte orchids, it is now scarce and expensive. Some experts still use it, but it may be difficult for beginners.
Diatomite is sedimentary rock of fossilized diatoms and is often used as a sole orchid medium. It’s porous, can hold 150% of its weight in water, is non-toxic and contains silica. Diatomite protects against rot, and can slowly release silica to orchids that love it. It is often used as a component in other orchid media.
Lava Rock doesn’t rot. It retains water, allows lots of air space for roots and provides great support. Lava rock can be used as a sole orchid medium, but you’ll need to be diligent about feeding and watering (drainage is fast). Lava rock often accumulates mineral salts. If your water contains a lot of minerals, lava rock may not be your best choice.
Tree Fern is porous and an excellent moisture-retaining, aerating orchid medium. It is also a good medium to pack around roots and to provide support for aerial roots.