Why does it have to be serile?

[The Viper]

The tropical rain forests that a lot of Orchids grow in are not realy sterile so why do we need to sterilize everything when we want to grow Orchid seeds at home?

[kavanaru]

easy... in the wild, most orchids seeds do not survive at all... you want, when you do the effort trying to propagate in vitro, to have some viable plants... therefore, you provide your seeds with high rich growing media (completelly different to what they find in nature), which is on the other hand a great place for fungi and bacteria. Fungi and Bacteria grow quicker than orchid seeds, so, if you allow them to grow together in a very rich medium, the Fungi and bacteria will overgrow your chids, and even "eat" them...

you can try growing with the very old method, of dispersing the seeds on wood, or on the culture pott of the parent plants... in this case, you do not need sterile medium, as you are imitating what happens in nature. However, the success rate of this method is very very very low.....

[Orchidaholic]

^ Kavanaru is completely correct! To add a little more... In nature the seed needs a specific fungal infection in order to germinate. It's kinda like the symbiosis of fungi and algae in lichens. A single capsule of orchid seeds can contain 10'000~1,000,000 seeds. Out of each capsule only a very few seeds reach maturity in the wild.
If done in a sterile environment we can have almost a 99% success rate

[maitaman]

Orchids need sugar to germinate. In nature it is found in natural secretions from several fungi and mosses. The other nutrients are from decomposing organic matter in the location and/or animal and bird droppings. Terrestrials here in Panama' have the added factor of volcanic soils in Chiriqui. The nutrients and sugars are in very small doses that do not encourage fungi and bacteria to nearly the extent of chemical cultures. In nature, the seedlings develop over a longer period of time due to the "less nutrients" factor.
(I've been without a comp - fried the hard drive - for a few days, but I'm B-A-A-C-K!)