There are at least 25,000 native species of orchids, according to Gustave Schoser, author of "Orchid Growing Basics." Orchids grow in warm tropical climates. Some prefer temperatures that vary only a few degrees from day to night. Others thrive with a 15 to 20 degree variance. Some prefer temperatures as cool as 60 degrees, while others, like phalaenopsis, prefer warmer spaces. Growing orchids in a terrarium allows you to control their environment.
Test the terrarium to make sure it's waterproof. Fill the bottom few inches with water, then empty it.
Wipe down the inside of the terrarium with a solution of 1 tsp. household chlorine bleach to 1 gallon of water. Let dry. This gets rid of any disease, mold or fungus that might be left over from previous plants.
Spread a 2 inch-thick layer of small stones on the bottom of the terrarium.
Put the orchids in their pots on the stones. Cover the pots with additional bark if you want to hide the pots.
Fill the terrarium with 1 inch of water. Do not let the water reach the bottom of the orchid pots. The water serves to increase the humidity. Orchids prefer humidity between 80 to 100 percent. If the pots are sitting in water, their roots will rot and they will die.
Place the terrarium where it will receive the light required by the type of orchid you've planted. A space that gets bright indirect light, but not hot sunlight, is a good choice for most orchids. Some orchids prefer more light than others.
Water the orchids by removing them from the terrarium and placing their pots in a container filled with room temperature distilled water for 30 minutes. Stir the water vigorously right before watering the orchids to add oxygen. Water once a week. Let the orchids drain for 30 minutes and then replace in the terrarium.
Fertilize the orchids once a month using a fertilizer specially developed for orchids.