Many species are quite common and occur in all three counties of the state, and in both the piedmont and coastal plain physiographic provinces.
Some species are very rare and are known from only a single, or a few localities in the state.
Ferns are found growing in a variety of different habitat types, such as marshes, swamps, on rocks, and attached to trees, but ferns are primarily forest dwellers preferring the shady moist soils of the forest floor. Ferns reproduce by spores and have a very different life cycle than the typical flowering plants that reproduce by seed. The differences between the true ferns and the fern allies are both sexual and asexual, but vegetative characteristics help to separate them in the field. The following are some of the more common species of ferns and fern allies that are found in Delaware. Nomenclature follows The Flora of North America, Volume 2, 1993.