Adiantum capillus-veneris

Some have preferred to divide this species into three infraspecific taxa: var. modestum in Arizona, New Mexico and Utah; var. protrusum from the approximate remainder of the U.S. range (Lellinger 1985); and in addition the typical variety. However, most authors disregard this varietal separation or imply that it is not helpful (e.g., Cronquist et al. 1972, Kartesz 1999). Plants counted in the eastern hemisphere have been diploid (2n = 60); in contrast, "several tetraploid counts have been reported from North America... Spore-measurement data, however, suggest that the polyploid cytotype may not be widely distributed" (FNA 1993).

Adiantum capillus-veneris is globally widespread in tropical and warm-temperate regions, including Eurasia, Africa, the West Indies, North America, Central America and South America (in Venezuela and Peru). The North American range includes roughly the southern one-third of the U.S., and within this range the species is fairly common and facing few threats.

This species is globally widespread in tropical and warm-temperate regions, including Eurasia, Africa, the West Indies, Central America and South America (in Venezuela and Peru). The North American range includes roughly the southern one-third of the U.S., with additional disjunct populations in South Dakota and British Columbia (Flora of North America Editorial Committee 1993). In North America, it is sometimes escaped from cultivation north of its natural range (Lellinger 1985, Gleason and Cronquist 1963). Populations in California may be introduced (Hickman 1993). Known in Colorado (Moffat, Mesa, Montrose, Ouray, Montezuma and Las Animas counties).

At least hundreds and possibly thousands of populations are extant rangewide, which is nearly cosmopolitan. Arkansas: common throughout the Ozarks (Arkansas Natural Heritage Commission); Kentucky: 31 occurrences documented, but several are general or unmappable records (Nick Drozda, pers. comm.); Georgia: documented in six counties (Georgia Natural Heritage Program); Mississippi: at least 100 populations likely, though the species is uncommon and has been documented in only two counties (Mississippi Natural Heritage Program); Missouri: widely scattered in appropriate habitat (Tim Smith, pers. comm.); Nevada: scattered in appropriate habitat in the south (Nevada Natural Heritage Program); Texas: locally common on seep zones and on creek banks in limestone canyons on the Edwards Plateau, hundreds to thousands of populations are estimated (Bill Carr, pers. comm.); British Columbia: one population known within a commercial resort development (British Columbia Conservation Data Centre); South Dakota: one occurrence, relatively stable since 1898 (David Ode, pers. comm.); Colorado: 12 known occurrences from five counties, but most have not been updated in over 30 years (Colorado Natural Heritage Program).

An individual knowledgable about 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.).

Although this species is common on the Edwards Plateau in Texas, no evidence of collection has been observed (Bill Carr, pers. comm.). The closely related species, Adiantum pedatum is on the United Plant Savers "To Watch List" (United Plant Savers 2000).

Seepages are the primary habitat of A. capillus-veneris. Seepages are vulnerable to changes in their water source, such as pollution or water diversion and loss. The threat of water diversion and loss is higher in arid regions, where water sources (including groundwater) are more coveted. In Kentucky, the impoundment of rivers and streams has inundated large areas of habitat for this species (Nick Drozda, pers. comm.).