CORK
   Wine corks are excellent for potting Aerides, Vandas, Ascocentrum and other orchids with large roots. They work very well in the slatted baskets.
   Cork nuggets which are about 1/2" in size can be added to bark or other mediums to help with drainage. There has been much controversy about the nuggets breaking down into a slimy mess.
   I personally have never used the nuggets. The cork slabs are excellent to mount your orchids to. They can be bought in many sizes and you can easily break them with your hands to the size you want.    I use this all the time and my orchids grow very well on it.

   Peat base mixes are very light and hold a lot of water.
The mix typically has some perlite and humus mixed with peat moss.
Straight peat moss is too fine to use for a number of orchids. When buying this medium, just ask for a "peat base potting mix."
   CAUTION! Peat base mixes can stay moist and cause root rot.
If you over water or you have problems with your pots not drying out, do not use this type of medium. If you live in a very dry area or do not water heavily then this would be a good medium to try.
   I would use it on the terrestrial orchids and those that like to be kept moist such as Paphiopedilums and Phalaenopsis.
   This mix should not be used with tree fern, cork or Osmunda. It can, however, be used with bark. Peat moss decomposes quite rapidly so you will need to repot more frequently when using these mixes.
COCONUT FIBER AND HUSK CHIPS

   These media are starting to pick up in popularity.
They hold moisture up to seven times its weight and will last for years. They are also very porous and easy to handle.
   The coconut fiber is excellent for lining baskets and for use with orchids that like to be kept moist such as Paphiopedilums. The husk chips are 1/4" to 1/2" in size and works very well in pots. It has been used for years in Holland for Cymbidiums and Phalaenopsis. The price for these mediums is very reasonable at this time. You can purchase it for around $1.00 a pound.
   You may read more about usig coconut husks and chips in cultivating orchids here and here.
ROCK WOOL

   Rock wool is a medium produced by spinning volcanic basalt rock in blast furnaces.
It has been used for years as an insulation in homes and buildings. Oil that is in the insulation type material is removed when the product is used for horticulture.
   It can be mixed with bark or used alone. This product lasts virtually forever and has very few problems with insects because it does not break down and decay when used alone. It can be purchased in cubes, mats and pellets.
   This product tends to pack tight so many growers will mix perlite or tree fern fiber with it to maintain an airy consistency.

   If you purchase Dendrobiums you have probably seen them potted in this medium.
It is a favorite medium in Hawaii for growing Dendrobiums. It retains water and never breaks down.
   Since Dendrobiums like to be in small pots but tend to grow tall, this medium helps the pots from tipping over.
   Lava rock is very airy and the roots seem to grow very well in it. The only disadvantage is it can accumulate salts so if your water contains a lot of minerals you must be careful using this.
   The price of this medium is very reasonable, however, if you have to have it shipped to you the price of the postage can be more than the price of the rock!
SHREDDED TIRES

Yes you are reading this correctly.
   In the past years there were continuing experiments using shredded tires as a potting medium. There is an article about this new medium in the November 1997 issue of the A.O.S. magazine (Orchids).
   I have been personally trying this media growing Odontoglossums, Cattleyas, Dendrobiums, and Phalaenopsis. The idea proved to be a very bad one - toxic materials present in volcanized rubber did harm these orchids, so forget shredded tires if you know what is good for them in the long run.
EXPANDED SHALE OR CLAY

   These are man-made products that are fired to form nuggets and the end product holds moisture and does not break down. Here are a couple of types.
ISOLITE^(tm)

   This is a cylindrical shaped porous ceramic material. It has up to 74% pore space which helps conserve water. Dendrobiums grow excellent in this medium and I have been using it for years.
   You can reuse this medium by baking it at 180 degrees ^oF (82 ^oC) in an oven. It does not attract insects and never needs to be replaced. Like many of the mediums that do not decay or break down, you can just move the whole plant into the next size pot without disturbing the root system.
ALIFLOR^(tm)

  Another man-made material that is like porous ceramic beads. These products are very similar to lava rock but much cleaner. These products are also used in hydroponics and water culture.