Ferns are vascular plants, meaning they have internal tubes for transporting fluids like all other plants besides true mosses and lichens. Ferns, however, reproduce by spores instead of seeds. Because of this they live in moisture-rich habitats and so are not likely found in dry, arid climates. In general, ferns can be distinguished from other low-growing species by their pinnate (divided into numerous branches or lobes on two sides of a common axis) leaves and a simple, narrow stem. There are five major characteristics to keep in mind when identifying a fern based on description.
Ferns in the Genera Botrychium have clusters of sporangia (spore sacs) on a leafless stalk that projects from the upper side of the frond. Common names of these are the grape and rattlesnake ferns. Botrychium lunaria and B. multifidum are two examples. These are not characteristic of what is usually thought of as the feathery fern shape as they have more stalk than leaves.
Some ferns, such as Blechnum spicant (deer fern) have once-pinnately divided fronds, meaning the individual leaves mirror each other on each side of the stalk, creating an even, swordlike shape overall. Polystichum munitum (sword fern) and Polypodium glycyrrhiza (licorice fern) also have once-pinnate leaves.
Two to Four Times Pinnate
Many ferns have fronds that are two to four pinnate, creating a more feathery and denser appearance. Cryptogramma crispa (parsley fern) has fronds that are two to three times pinnate, Gymnocarpium dryopteris (oak fern) is two to three times pinnate and Thelypteris phegopteris (narrow beach fern) is twice pinnate.
Some ferns stay green year-round. When hiking in the spring, and the newly uncovered ground shows itself, you can see that these ferns have maintained their green color through the cold months. Pityrogramma triangularis (goldenback fern), Botrychium multifidum (leathery grape fern and the aforementioned deer fern, licorice fern and parsley fern are examples of evergreen ferns.
Fewer ferns grow that are deciduous. Examples of ferns with deciduous fronds, which turn brown and die each fall and regenerate in the spring, are Botrychium lunaria (common moonwort), (green spleenwort) and Adiantum pedatum (maidenhair fern).