Because charcoal can allow air passing through compared to soil. The idea is to allow the the internal part of the root to dry and prevent them rot.
good ventilation and disease resistent Answer In addition to the above the Orchids grown in bark or spaghnum moss with charcoal through it are usually epiphytes therefore they would not grow in soil as excellent drainage is required.
The mix I use to pot my orchids in is about 50 percent activated charcoal.
Not all Orchids need to grow on trees, only the epiphytes, terrestiall Orchids grow in the soil.
how many orchids are there in the world
they grow faster on charcoal
The wealthy began growing orchids in the midninteenth century in greenhouses to mimic native conditions. They had to learn to have ventilation to best grow the orchids.
some types of flowers are orchids and bromeliads
less ephilyte orchids are often grown on coconut husk
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Somewhere in Thailand
hibiscus, and morning glory grow singly