Adiantum pedatum

As treated here, excludes Adiantum aleuticum, formerly treated as various varieties of A. pedatum, incl. vars. aleuticum and calderi. See treatment by C.A. Paris in Flora North America (vol. 2, 1993); Kartesz (checklist, 1994; floristic synthesis, 1999) treats the complex similarly. A. pedatum is now considered a species of deciduous woodlands in eastern North American only. A. aleuticum is primarily western, but occurs rarely in the East on serpentine. A. viridimontanum is a fertile allotetraploid derived from hybridization of these two species, and known only from Vermont and Quebec.

This was once believed to be a single species that occurred with taxonomic variation in a wide range of natural community types, and occurred in eastern Asia and throughout much of North America. Now these populations are viewed as three species in North America alone: A. aleuticum which occurs from Alaska down into Mexico, with a few disjunct populations scattered from Newfoundland to Maryland (primarily or exclusively on serpentine); A. pedatum which occurs in forests in the approximate eastern half of the U.S.; and A. viridimontanum, an allopolyploid species arising from A. aleuticum and A. pedatum (Flora of North America Editorial Committee 1993, Gleason and Cronquist 1963), which is confined to Vermont and Quebec according to Kartesz (1999).

This species is common to ubiquitous in mesophytic forest communities throughout the eastern U.S. and Canada. Collection of this species from wild populations and other threats do not seem to pose a significant danger to this species at this time.

Adiantum pedatum is found in roughly the eastern half of the United States, occurring from Minnesota to Maine and Nova Scotia, and south to Oklahoma, Louisiana, and Georgia (Flora of North America Editorial Committee 1993, Kartesz 1999).

Many thousands of populations are extant rangewide. Indiana: common in mesic forests throughout the state, encountered routinely in appropriate habitats (Indiana Natural Heritage Data Center); Michigan: common in mesic forests throughout the state (Michigan Natural Features Inventory); New York: very common, thousands of occurrences (New York Natural Heritage Program); British Columbia: common (British Columbia Conservation Data Centre); Kentucky: common in a variety of mesophytic woodland communities throughout the state (Nick Drozda pers. comm.); Georgia: secure (Georgia Natural Heritage Program); Mississippi: widespread in north, documented in 17 counties (Mississippi Natural Heritage Program); Missouri: common and widespread (Missouri Department of Conservation); Maine: uncommon but not rare, known from 15 of 16 counties (Maine Natural Areas Program); Delaware: 55 extant populations documented (Delaware Natural Heritage Program); New Hampshire: not rare (New Hampshire Natural Heritage Inventory).

An individual with the U.S. herbal medicinal industry states that trade in the plant is minor, on the order of 150-300 pounds per year, and that it is probably the aboveground parts that are utilized (McGuffin pers. comm.).

In Michigan, it is likely that there is at least casual collection for personal gardens and the like, because of the attractiveness of this fern (Michigan Natural Features Inventory). There are currently no reports that individual populations have been negatively impacted or extirpated due to collection for the plant trade.

This species is on the United Plant Savers "To Watch List" (United Plant Savers 2000).

In Kansas, the primary threat to this species is habitat fragmentation of the maple-basswood and mesic oak-hickory forests, and habitat degradation (Craig Freeman pers. comm.). In Michigan, there are probably some threats due to logging, however, this species is still quite common and is unlikely to become seriously threatened in the future (Mike Penskar pers. comm.).