About 80 percent of orchids are from the tropics in both the New World (Central and South America) and the Old World (Asia and Malaysia). A smattering can be found in North America and Europe.
The ones that grow in your home, though, are all of tropical or semitropical origin. They mostly hail from areas of high rainfall and humidity and enjoy tropical to above-freezing temperatures during the winter.
Orchids are divided into two major categories based on where they grow. Those that are commonly found clinging to branches of trees are called epiphytes; those that thrive growing on or in the ground are called semiterrestrials and terrestrials.
So how can you tell the difference between the two? Many of the terrestrial roots are hairy, like those found in the slipper orchid (see Figure 1-2). Epiphytes have thick roots (called aerial roots because they’re frequently suspended in the air), which are covered with a silvery material called velamen, which can absorb moisture from the air like a sponge.