Bark simulates the natural way orchids grow on trees.

The bark available for orchids should have been “steamed” before use to extract the resins that can be toxic to orchids; however, the truth is you never know what you buy.  By removing that resin the water-holding capacity of the bark increases and its life span decreases. Orchids growing on bark will need re-potting every 12 months. Adding charcoal will keep the bark OK for up to 24 months. Off course, some growers re-pot their orchids every ten years.

Bark is good for seedlings and small orchids. Cattleyas grow well in bark.

The preferred woods are the coniferous trees Douglas fir, Pinus radiata, and Redwood.

Douglas fir is the most popular bark of the three. It is inexpensive, fairly light and easy to handle. It has a rough surface, it does not compact easily, allows air and water to be circulate freely, and be purchased in varied sizes from very small to very large pieces. On the negative site: After the “steam” treatment and with the raisin removed, colonies of nitrogen consuming micro-organisms take over and extra Nitrogen is needed. The microorganisms are also causing the decay of the bark. As it decays it may compact and unless re-potted, the roots may rot.

Redwood bark is similar to fir bark but more resistant to decay. It costs more and it is less common. It supposed to be the best of the woods mentioned but nobody talks about redwood anymore.

Pine bark (Pinus radiata) is sourced from renewable Pine forests. New Zealand allegedly produces and exports all over the world Pine bark. I do not know much about the New Zealand Pine Bark. If the claims made are true it must be good; however, I am told it is un-treated.

I know experienced growers, persons I respect for their knowledge, that boil in water the pretreated bark they buy before use. Many wash the bark before use. I only sieve the bark to remove the fines and then add the fines in my terrestrial potting mixes.

If you are tempted to use your “own bark”, make sure you steam or boil it before use.

Primarily, bark is mixed with charcoal and Perlite.