Orchids

Depends on the type of Orchid. Hardy? Terrestrial? Epiphytic (growing on trees). All of them like a an open compost and the epiphytes need a special compost but you could try medium grade chipped bark.. I think you need advice from some one else, it would help to know which kind you want to grow.

recently acquired knowledge - orchids get their nourishment via aerial roots from the air, only need very little nourishment, just water.

There are 50000 species of Orchid the largest family of flowering plant after the grasses. Terrestrial orchids would represent a smaller proportion of the family and grow in all types of soil from peat to sand and are present on every continent apart from Antarctica take your pick- better still seek out a specialist terrestrial grower and by the way they are not cheap and people wont think twice about stealing them if they get a chance either wild growing or in your garden! - ENJOY