Rare Species Guide

  Basis for Listing

The geographic range of Botrychium mormo (goblin fern) is confined to forests in portions of three contiguous states (Minnesota, Wisconsin, and Michigan) and in Quebec Canada, with most of the records coming from north-central Minnesota (Laurentian Mixed Forest Province), particularly the Chippewa National Forest (Cass and Itasca counties). However, the species is scarce even within its stronghold, and it is becoming increasingly rare. Botrychium mormo requires an intact tree canopy in order to have consistently shaded and moist conditions, and the accelerating rate of habitat degradation is the reason for its decline. While concerns over habitat loss and degradation from timber management activities and land clearing prompted the listing of B. mormo as special concern in 1984, an even more insidious threat has emerged in recent years.

The invasion of non-native earthworms is apparently responsible for an accelerating and alarming rate of habitat degradation. The worms, which were introduced from Europe, rapidly consume the humus layer of the soil, thereby rendering the habitat unsuitable for B. mormo (Mortensen and Mortensen 1998; Gundale 2002). A significant, albeit precisely unknown, number of populations of this fern have disappeared within the last decade, and the trend appears to be continuing. Consequently, the status of B. mormo was elevated to threatened in 2013.

  Description

Botrychium mormo is a small plant, no more than 9 cm (3.5 in.) tall. It has a single leaf, divided into 2 segments. The sterile segment is about 2 cm (0.75 in.) long and 0.5 cm (0.20 in.) wide, with 1 - 3 pairs of round-pointed or truncate lobes. The fertile segment is about 4.5 cm (1.75 in.) long. The sporangia are large and sunken and do not open until late September. The species is unlikely to be mistaken for any other moonwort except B. simplex (least moonwort); however, the outer pinnae of B. mormo are squarish and have a coarsely toothed margin. Also, the tip of the sterile section of the leaf in B. mormo is clearly divided into blunt segments.

  Habitat

Botrychium mormo occurs in mature mesic hardwood forests, where the dominant trees are Acer saccharum (sugar maple), with lesser amounts of Thuja occidentalis (northern white cedar) and Tilia americana (American basswood). The canopy must be intact to maintain shaded and moist conditions. The soils are loamy, with large amounts of humus or organic matter on the surface.

  Biology / Life History

Being a fern, B. mormo has two separate life stages. The relatively large aboveground sporophyte produces spores that have half the number of chromosomes of the parent sporophytes. These spores are very small and are capable of being dispersed by wind, though there has been no direct measurement of how far the spores actually travel. These spores germinate underground and grow into the gametophyte stage. This is the sexual reproduction stage, but gametophytes are seldom seen due to their small size and underground habitat.

Botrychium mormo emerges above ground in June and, according to one study, the population size peaks in early July, with the largest plants appearing late in August (Johnson-Groh and Lee 2002). It has been suggested that the appearance of the largest plants late in the season had previously caused field workers to believe that this was a late-season species (Johnson-Groh and Lee 2002).

  Conservation / Management

Botrychium mormo requires mature mesic hardwood forests that have a history free from major human disturbance. In this regard, management is fairly simple - protect habitat from activities that open the canopy or disturb the soil. A more insidious threat has emerged in recent years that is more difficult to deal with: non-native earthworms. An infestation of worms can very quickly remove nearly all the humus from the soil, rendering it unsuitable for B. mormo.

  Best Time to Search

Finding and identifying Botrychium mormo can be difficult because of its small size and sporadic appearance above ground. The best time to search is during the months of July and August.

  Conservation Efforts in Minnesota

The greatest number of B. mormo in Minnesota (and possibly the world) are found in the Chippewa National Forest. The U.S. Forest Service is aware of this and has placed B. mormo on their sensitive species list (Casson et al. 1994). For species on this list, the Forest Service is required to "…implement a program to conserve…plants…to insure their actions do not jeopardize the continued existence of any threatened or endangered species or result in the destruction or adverse modification of critical habitat".

  Authors/Revisions

Welby Smith (MNDNR), 2008 and 2018

(Note: all content ©MNDNR)

  References and Additional Information

Casson, J., I. Shackleford, L. Parker, and J. Schultz. 2002. Conservation approach for Goblin Fern (Botrychium mormo, W. H. Wagner). USDA, Forest Service, Eastern Region, Milwaukee, Wisconsin. 31 pp.

Casson, J., J. Mathisen, and P. Strong. 1994. A conservation strategy for the Goblin Fern (Botrychium mormo) on the Chippewa National Forest. Unpublished report, USDA, Chippewa National Forest, Cass Lake, Minnesota. 21pp.

Chadde, S., and G. Kudray. 2001. Conservation assessment for Botrychium mormo (Little Goblin Moonwort). U.S. Forest Service, Eastern Region, Milwaukee, Wisconsin. Accessed 16 September 2009.

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

Gundale, M. J. 2002. Influence of exotic earthworms on the soil organic horizon and the rare fern Botrychium mormo. Conservation Biology 16(6): 1555-1561.

Johnson-Groh, C., and J. M. Lee. 2002. Phenology and demography of two species of Botrychium (Ophioglossaceae). American Journal of Botany 89:1624-1633.

Minnesota Department of Natural Resources. 2003. Field guide to the native plant communities of Minnesota: the Laurentian mixed 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. 352 pp.

Mortensen, S., and C. Mortensen. 1998. A new angle on earthworms. Minnesota Conservation Volunteer 61:20-29.

Penskar, M. R., and P. J. Higman. 1996. Special plant abstract for Botrychium mormo (goblin moonwort).
Michigan Natural Features Inventory, Lansing, Michigan. . Accessed 16 September 2009.

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

U.S. Forest Service. 2008. Superior National Forest rare plant guide: grape-ferns & moonworts [web application]. U.S. Forest Service, Region 9, Superior National Forest, Duluth, Minnesota . Accessed 12 June 2009.

Wagner, W. H., Jr., and F. S. Wagner. 1981. New species of moonworts, Botrychium subg. Botrychium (Ophioglossaceae), from North America. American Fern Journal 71(1):20-30.

Wagner, W. H., Jr., and F. S. Wagner. 1993. Botrychium. Pages 86-101 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 2. Oxford University Press, New York, New York.