American Hart's-Tongue Fern
(Asplenium scolpendrium var. americanum)
This fern can
be found in climates as different as Canada and Alabama, suggesting
that it had spread widely since the last ice age.
Habitat: This fern is found in close
association with outcrops of dolomitic limestone, in coulees, gorges
and in cool limestone sinkholes in mature hardwood forests. It requires
high humidity and deep shade provided by mature forest canopies or
overhanging rock cliffs. It prefers soils high in magnesium.
It's Threatened: Although
this plant is found over a very wide area, from Alabama to Canada,
its populations tend to be very small and isolated due to its unique
habitat. Because of its natural rarity, it is particularly vulnerable
to disturbance. Many activities threaten the American hart's-tongue.
Quarrying, recreation and residential development have all destroyed
these plants and their habitat. Canadian populations are threatened
by lumbering and the development of land for ski resorts and country
estates, among other activities. By removing shade trees, logging
raises light levels and lowers humidity, decimating any American hart's-tongue
ferns in that area.
Midwest Endangered Species