Ferns are an early evolutionary lineage of plants, which reproduce by spores (like mosses), and whose specialized vascular tissues are used for conducting water and nutrients (like conifers and flowering plants).
Fern leaves (also called fronds) arise directly from an underground stem (called a rhizome) or a very short vertical stem at ground level. Ferns do not produce flowers or seeds, but rather reproduce via tiny spores produced in specialized structures called sporangia, which are usually located on the underside of the fronds. In some species the sporangia are produced on conspicuously modified portions of the leaf (e.g. leaf tips in the Royal Fern [Osmunda regalis]), or the entire leaf is modified into a spore-producing structure, as in the Cinnamon Fern (Osmunda cinnamomea). Leaves producing sporangia are called fertile fronds, and those not producing sporangia are called sterile fronds.
One of the first checklists of ferns for NYC, published in 1819 by John Torrey, listed 60 indigenous ferns, horsetails and lycophytes. Today, at least 16 of the 60 species mentioned in the 1819 checklist are locally extinct. These may occur in some abundance outside NYC, but they have not been documented in the five boroughs in the last 30 or more years (sometimes for more than a century). Another six are possibly historical, having been reported in the City recently, but their presence must be checked and confirmed. 11 species are classified as “rare”: these are currently known from only one population in the City. 10 species are classified “infrequent” because they are known from more than one, but five or fewer populations. 19 species are “frequent”– known from more than five populations. The Blunt-Lobed Woodsia (Woodsia obtusa) and the Ebony Spleenwort (Asplenium platyneuron) are our two most common ferns – both commonly grow on walls. There have been no modern treatments of the ferns of NYC, although there have been publications which consider the state of New York as a whole (such as the Atlas of New York Ferns (1984)).
Learn more about our local fern diversity using the links below!