There are 10,400 known species of true ferns. They are commonly found in wet climates, with about 70 percent of species living in tropical regions, and most of the rest in temperate zones—although a hardy few actually live in the desert or the Arctic. Ferns come in a wide variety of shapes, textures, colors, and sizes. Some tree ferns can reach heights of more than 40 feet tall, while tiny aquatic ferns may only measure a few inches. Humans have used ferns for fertilizer, medicine, food, and decoration. In their native habitats, ferns serve an important purpose in stabilizing soil and preventing erosion, and they can thrive in places where many other plants won’t do well.
Ferns are so different from flowering plants that a different terminology is used to describe them. The part of ferns we see most is called the frond, which has two main parts: the stipe (similar to the stalk in other plants) and the blade (the leafy portion). The blade may be solid or divided into various numbers and arrangements of leaflets, which is one way to identify different species.
Instead of stems, ferns have rhizomes, which are often small and inconspicuous or even mostly underground—people sometimes confuse them with roots. In some species, the rhizomes spread out in a network to support the plant. Tree ferns, however, have a thick, tall rhizome that grows aboveground like the trunk of a tree. Last but not least, a fern’s roots grow down from the rhizome, or sometimes the stipe. They usually do not branch out, but rather serve to anchor the plant while absorbing water and minerals.
The reproductive structures of ferns are called sporangia, and a group of several sporangia together is called a sorus (plural sori)—these are the bumps you see on the underside of fronds. The arrangement or pattern of the sori varies and is another way to identify different fern species. Sporangia are miniature sacks that produce the spores. When the sporangia are mature, they burst, releasing spores into the wind that are carried to a new location. The sporangia release millions, even billions, of spores over the lifetime of a fern, but most do not encounter suitable conditions for growth. If a spore is lucky and lands somewhere with proper moisture and light, it will eventually become a new fern.