LAVA ROCK (lava)
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 (photo)
Yes you are reading this correctly. In the past couple of years there are 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). For the last 10 months, I have been personally trying this media growing Odontoglossums, Cattleyas, Dendrobiums, and Phalaenopsis. So far, there have been no ill effects. The plants have accepted the media and have produced good root growth. I use a balanced fertilizer (23-19-17 or 7-9-5). The media does not break down so it has no problems with insects. This product does retain moisture which surprised me. PLEASE remember this product is still in the experimental stages. The price is very reasonable but the shipping is quite expensive due to the weight of this product. It usually comes in 1/4" to 1/2" pieces.
EXPANDED SHALE OR CLAY (photo)
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. Dedrobiums grow excellent in this medium and I have been using it for years. You can reuse this medium by baking it at 180 degrees F (82 C) 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 with out 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.
In the previous article as well as this one, I have covered a large number
