For reproduction, orchids have male and female parts joined together into a column. This structure is the most important characteristic that identifies the orchid family.

Not all orchids grow from the ground. Some are “air plants” that grow on trees. Unlike parasites, however, they do not rob the trees of important nutrients.

Orchids grow in a lot of places. But some areas have more orchid species than others. For example, Costa Rica has about 1,500 species. The United States has about 70. Even Greenland has a few.

Some people can easily recognize common orchid plants. The Cattleya, for example, gets a lot of attention.

A white Cattleya is one of the first orchids visitors see as they enter the tropical jungle area of the United States Botanic Garden in Washington, DC. The plants have soft white petals with yellow at the center, and people stop to smell the flower. One recent visitor said it looked just like a bird. Another said, no, it was similar to a beautiful insect, the butterfly. Other people believe it looks like a star.

The white Cattleya is sometimes called the corsage orchid. People wear the cut flower on clothing to mark special events like birthdays or Mother’s Day parties. There are many species of Cattleya. Most come from the treetops in wet tropical forests in Central and South America.

But many orchids are strong. Orchid expert Tom Mirenda says some can grow in deserts or in wet, swampy grasslands. He says others can live on coastlines and on islands made of limestone coral. A few can live on salty seawater spray. Mr. Mirenda says orchids can even grow along rivers and streams, where water may cover them at times.