Ferns are flowerless green plants. They are usually easy to recognize by the featherlike shape of their leaves, which are called fronds. Ferns reproduce by spores rather than by seeds. Some plants that are called ferns, such as asparagus ferns, reproduce by seeds and are not true ferns.
There are about 12,000 different species, or types, of fern throughout the world. Some types first appeared on Earth more than 360 million years ago. Ferns commonly grow in tropical rainforests. They also grow in other warm, moist places where there is plenty of shade. Very few species of fern are found in dry, cold places.
Many fern species grow on the trunks and branches of trees. Others grow in bogs and marshes or float on the surface of ponds. Some types of fern, called bracken, spread like a weed through fields and pastures.
The smallest ferns are only a fraction of an inch tall. The largest ferns measure from 30 to 80 feet (10 to 25 meters) tall. Young fern leaves are tightly curled. When they grow and begin to unfurl, they resemble the neck of a violin.
Ferns grow millions of cells called spores on the underside of their leaves. These spores scatter into the air. A small number of them fall on damp surfaces and soils. They grow into tiny, kidney-shaped structures. These structures produce male and female cells, which together produce a new fern.
People often use ferns to decorate their homes and gardens. Such animals as deer eat ferns, and some birds use them to line their nests.
