Orchid roots

[Mike O'C]

Guys, not sure if this is the right forum to post this query but if not I apologise.
My preference for growing orchids is in pine bark in a clay pot. Lately I have topped it off with a layer of sphagnum moss. Other growers here prefer a cultiwool (rockwool)/polystyrene mix in plastic pots. Whenever I buy a plant at out local society I always repot out of that mixture. I have noticed that in the cultiwool mix and in my bark/sphagnum mix the plants produce very few roots and in my collection the roots do not penetrate the bark but stay in the sphagnum. The question is do orchid plants produce roots proportional to the water content of the medium. Some of my plants with few roots actually topple over as they are not anchored down.