Asplenium scolopendrium var. americanum
|American fern, American hart's tongue fern, Hart's-tongue fern|
|(Fern.) comb. nov. ined.|
|Brian Parsons and Roger McCoy|
The following Participating Institutions are custodians for this species in the CPC National Collection:
The Holden Arboretum
The conservation of Asplenium scolopendrium var. americanum is fully sponsored.
Brian Parsons and Roger McCoy contributed to this Plant Profile.
Asplenium scolopendrium var. americanum, or American hart's tongue fern, is the North American variety of a European species that was described in 1753 by Linnaeus as Phyllitis scolopendrium. This variety was discovered in North America in 1849 in Tennessee, and since then has been found in Alabama, New York, Michigan, and Ontario Canada. The American hart's tongue fern differs from its European relative based on several distinct morphological (shorter fronds, fewer indusia, etc. (Fernald 1935)) and genetic features (144 rather than 72 chromosomes (Britton 1953)). (USFWS 1989)
American hart's-tongue fern forms rosettes of evergreen, undivided fronds, 5 - 17 inches long (12 - 42 cm), - 1 inches wide (2 - 4.5 cm) with two lobes at the base, making the base heart-shaped. The green petiole portion of this frond is from 1 to 5 inches (3 to 12 cm) long, with cinnamon-colored scales on its surface. Fronds arise in clusters from short, creeping rhizomes that are themselves covered in cinnamon-colored scales. (USFWS 1989) Plants produce new fronds in the spring; each frond survives for two growing seasons, producing spores on year-old fronds from May through August. Spore-producing structures, the sporangia, are grouped into small, linear sori found on the upper half of the lower surface of the frond.
Distribution & Occurrence
- New York
American hart's-tongue fern occurs at sites on or near dolomite (magnesium-rich limestone) that remain consistently moist year-round, such as sinkholes, cave entrances, wooded limestone ravines and talus slopes, and steep north-facing slopes with rich, moist soil. Within these sites, it is typically found in microhabitats such as moist crevices, moss mats, depressions, spray zones, and shady cliff margins (NatureServe 2008).
Young plants are more vigorous when they grow at the edges of canopy gaps where they receive filtered sunlight; both deep shade and strong direct sunlight are detrimental. At its more northern sites, American hart's-tongue fern is affected by the amount and duration of snow cover: insufficient snow leads to desiccation and cold damage while prolonged springtime snow cover, such as accumulations on lower slopes, limits access to spring sunlight (Cinquemani Kuehn and Leopold 1993).
|Approximately 134, as follows:
Alabama - 2 occurrences, one protected
Michigan - 5 occurrences, 3 of which are protected
New York - 16 occurrences, 8 of which are protected
Ontario - 110 occurrences, 38 protected
Tennessee - one occurrence, protected.
Conservation, Ecology & Research
At sites in Tennessee and Alabama, the American hart's-tongue fern occurs in sinkholes where temperatures are cooler and humidity levels are higher (NatureServe 2008). At these southern sites, typical associates include stinging nettle (Urtica dioica), jack-in-the-pulpit (Arisaema triphylla), elderberry (Sambucus canadensis), northern maidenhair fern (Adiantum pedatum), bulblet fern (Cystopteris bulbifera), Tennessee bladder fern (C. tennesseensis), black-stem spleenwort (Asplenium resiliens), walking fern (Asplenium rhizophyllum = Camptosorus rhizophyllus), and glade fern (Athyrium pycnocarpon = Diplazium pycnocarpon). Associated bryophytes and liverworts include Palamocladium laskeoides, Mnium hornum, M. affine, Campylium hispidulum, Thamnobryum allegheniense, Plagiochila austinii, Conocephalum conicum, and Entodon macropodus.
removal of shrubs and small trees
erosion and collapse of sinkholes
poaching and overcollection
Kelsall et al. (2004) analyzed census data for New York populations of American hart's-tongue fern in light of climate data and determined that climate variables have little effect on distribution and population size; they concluded that the ability of habitat to buffer plants from the effect of climatic fluctuations is important.
Because of the importance of mosses to the reproductive success of American hart's-tongue fern, management for ground-layer bryophytes is recommended (NatureServe 2008).
Poaching by fern collectors has had a negative effect on American hart's-tongue fern populations; every effort should be made to limit access by collectors and to keep location information confidential (NatureServe 2008).
The Tennessee population is protected by a conservation easement held by The Tennessee Chapter of The Nature Conservancy; there is no active management occurring at the site (NatureServe 2008).
Access by spelunkers is restricted to caving permit holders at the Alabama site on Forest Service land; however, plants at this site have not been seen in several years and may be extirpated. Alabama does not directly protect endangered and threatened plants. However, American harts-tongue is protected as a form of cave life by the Alabama Cave Conservation Act of 1988 (NatureServe 2008).
Most of the New York plants occur within a single state park, where they receive protection; plants at another New York park were adversely affected by trail construction in the 1950's and subsequent erosion has eliminated many of the plants. Two Michigan populations have been purchased by a conservation organization to protect this species. One Michigan population on U.S. Forest Service land was provided some protection when forest managers rerouted a trail that traversed the population (NatureServe 2008).
Conduct long-term demographic studies in permanent plots located within each site
Assess effects of climate change on populations
Determine effect of canopy thinning
Determine specific reproduction and survival requirements
Assess the degree of genetic variability between and within populations in order to determine which populations are essential for protection
Assess impacts of spelunking, hiking, and other recreational activities on populations
Flora of North America Editorial Committee. 1993. Flora of North America north of Mexico, Vol. 2, Pteridophytes and gymnosperms. New York. Oxford Univ. Press, .
Foster, F.G. 1993. Ferns to Know and Grow. Portland: Timber Press.
Kral, R. 1983. A report on some rare, threatened or endangered forest related vascular plants of the south, USFS technical publication R8-TP2. Atlanta, GA. U.S. Forest Service.
Lellinger, D.B. 1985. A field manual of the ferns and fern allies of the United States and Canada. Washington, D.C.: Smithsonian Institution Press. 389p.
Shaver, J.M. 1954. Ferns of Tennessee. Nashville, TN: George Peabody College for Teachers Bur. of Publ. 502p.