Rare Species Guide

  Synonyms

Thelypteris hexagonoptera, Dryopteris hexagonoptera

  Basis for Listing

Phegopteris hexagonoptera (broad beech fern) is a distinctive and comparatively conspicuous woodland fern. It is widespread in the eastern United States, but in Minnesota it is restricted to a small area of The Blufflands in the southeastern corner of the state. When P. hexagonoptera was listed as special concern in 1984, it was known by a total of five records from Houston, Fillmore, Wabasha, and Winona counties (Ownbey and Morley 1991). Subsequent to that time, botanical surveys were conducted in these and several adjacent counties, and only one new occurrence was found.

For this reason, the species’ status was changed to threatened in 1996. Subsequent searches, in what were believed to be the best surviving habitats, again failed to find any additional populations, and only one historic record has been reconfirmed on the ground. For these reasons, its status was changed to endangered in 2013.

There is great concern that sensitive forest species in southeastern Minnesota are in greater jeopardy than previously thought. Threats from non-native invasive plants, such as Alliaria petiolaris (garlic mustard); non-native invasive animals, such as earth worms (Frelich 2006); and unnaturally high population levels of White-tailed Deer (Odocoileus virgineanus) are putting unprecedented pressure on our rarest native species.

  Description

Phegopteris hexagonoptera is a perennial fern, with broadly triangular pinnate-pinnatifid fronds that grow from 25 to 75 cm (10-30 in.) tall. The frond blades are between 15 and 30 cm (6-12 in.) wide and about as long as wide. They are not evergreen. The fronds grow closely spaced along an underground stem (rhizome) that is slender and scaly. Phegopteris hexagonoptera has a winged rachis (main axis), which is the primary difference between it and other fern species with which it might be confused (Smith 1993).

  Habitat

In Minnesota, P. hexagonoptera occurs in rich and moist soil, primarily on north-facing mesic hardwood forested slopes dominated by Acer saccharum (sugar maple), Quercus spp. (oak species), or Tilia americana (basswood).  Because of the paucity of records from Minnesota, habitat details are few.

  Biology / Life History

Phegopteris hexagonoptera is a perennial fern that reproduces both asexually and sexually. Asexual reproduction occurs via branching of the rhizome, which primarily serves to enlarge a particular colony or clone. It does not allow the species to colonize new habitats or disperse from one location to another.

Sexual reproduction is accomplished in the customary manner of ferns. Tiny spores, which appear on the undersides of fertile fronds in late summer or fall, can be transmitted by wind over great distances. If a spore lands in a suitable environment, a gametophyte may form. A gametophyte is a small formless structure that lives entirely underground. The gametophyte has both male and female reproductive parts, and if fertilization is achieved, the result is the sporophyte stage. This is the familiar leafy stage that most people recognize as a fern.

  Conservation / Management

Known locations for this extremely rare species need to be managed to maintain the tree canopy and the cool and moist understory conditions that are characteristic of this habitat type. It is also essential to exclude domestic livestock to prevent trampling and to monitor the habitat regularly to prevent the establishment of invasive species.

  Best Time to Search

The best time to search for P. hexagonoptera is when the frond is fully developed, from May through August.

  Conservation Efforts in Minnesota

The Minnesota Biological Survey has been completed in the known range of this species in the state.

  References and Additional Information

Breakey, E. W., and R. I. Walker. 1931. Preliminary reports on the flora of Wisconsin. No. 12 Polypodiaceae. Transactions of the Wisconsin Academy of Science, Arts and Letters 26:263-273.

Coffin, B., and L. Pfannmuller, editors. 1988. Minnesota's endangered flora and fauna. University of Minnesota Press, Minneapolis. 473 pp.

Frelich, L. E., C. M. Hale, S. Scheu, A. R. Holdsworth, L. Heneghan, P. J. Bohlen, and P. B. Reich. 2006. Earthworm invasion into previously earthworm-free temperate and boreal forests. Biological Invasions 8:1235-1245.

Gleason, H. A., and A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. Second Edition. New York Botanical Garden, Bronx, New York. 910 pp.

Minnesota County Biological Survey. 1994. Natural communities and rare species of Houston County. Minnesota County Biological Survey Biological Report No. 50. Minnesota Department of Natural Resources, St. Paul.

Minnesota County Biological Survey. 1994. Natural communities and rare species of Winona County. Minnesota County Biological Survey Biological Report No. 49. Minnesota Department of Natural Resources. St. Paul.

Minnesota Department of Natural Resources. 2005. Field guide to the native plant communities of Minnesota: the eastern broadleaf forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 394 pp.

Minnesota Department of Natural Resources, Division of Ecological Resources. 2008. Rare species guide: an online encyclopedia of Minnesota's rare native plants and animals [Web Application]. Minnesota Department of Natural Resources, St. Paul, Minnesota. Accessed 1 July 2009.

Minnesota Department of Natural Resources, Division of Fish and Wildlife. 1995. Statement of need and reasonableness in the matter of proposed amendment of Minnesota Rules, Chapter 6134: endangered and threatened species. Minnesota Department of Natural Resources, St. Paul, Minnesota. 336 pp.

Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis. 320 pp.

Peck, J. H. 1982. Ferns and fern allies of the driftless area of Illinois, Iowa, Minnesota, and Wisconsin. Milwaukee Public Museum Press Contributions in Biology and Geology No. 53, Milwaukee, Wisconsin. 140 pp.

Smith, A. R. 1993. Phegopteris. Pages 221-222 in Flora of North American Editorial Committee, editors. Flora of North America north of Mexico. Volume 2. Oxford University Press, New York, New York.

Smith, W. R. 2023. Ferns and lycophytes of Minnesota: the complete guide to species identification. University of Minnesota Press, Minneapolis. 368 pp.