Rare Species Guide

  Synonyms

Disporum trachycarpum

  Basis for Listing

Prosartes trachycarpa (rough-fruited fairybells) was first found in Minnesota at a single site in northern Cook County in 1999 (Gerdes 2001). There were approximately 60 plants scattered across about 80 m (262 ft.) of semi-open forested ridge-top (Border Lakes Subsection). This was a truly remarkable discovery; it remains, to this date, the only known occurrence of this species in Minnesota. Similar habitats in the region have been intensively searched, before and after 1999, but no other populations of P. trachycarpa have been found.

Prosartes trachycarpa typically occurs in the northwestern and western regions of the U.S. and Canada (Utech 2002). According to Judziewicz et al. (1997), the nearest populations of this species to Minnesota are James Bay, Ontario; Pembina County, North Dakota; and Isle Royale, Michigan. In Michigan, P. trachycarpa is listed as threatened (Michigan Natural Features Inventory 2007).

Of primary concern is the fragility of the habitat where the population occurs. The soils are loose and prone to erosion or dislocation; they are held together only by lichens and the roots of small grasses and sedges. As such, the primary threat to the species is non-compatible recreational activities. This is evidenced by a recent proposal to put a hiking trail precariously close to the only known population. A single disturbance or random event could potentially cause the extirpation of this species in Minnesota. An additional concern is the changing nature of the vegetation at the site. The aging jack pine canopy is breaking-up, and shrub cover and competition has increased in response to the increased light; in areas like this, robust groups of plants are gone or seriously declining.

This information presents a remarkable picture of a rare and long-range disjunct population of an ecologically sensitive plant species. It is difficult to know for certain whether this is the first appearance of a species with an expanding range, or the last appearance of a species with a contracting range. Either way, the significance of the occurrence is clear; hence, Prosartes trachycarpa was listed as an endangered species in Minnesota in 2013.

  Description

Prosartes trachycarpa is a herbaceous perennial “wildflower” that grows to a height of 30-80 cm (12-32 in.). The stems are sparingly branched above the middle. The leaves are 4–12 cm (1.6-4.6 in.) long and 2–5 cm (0.8-2.0 in.) wide. The blade of the leaf is ovate to oblong-lanceolate in shape; it is attached directly to the stem, without a petiole. The upper leaf surface and leaf margins are moderately hairy. The leaf surface has 7-9 prominent parallel veins. There are clusters of 1-3 bell-shaped flowers at the ends of short branches; the petals and sepals are creamy to greenish white in color, narrowly oblanceolate in shape, and 8–15 mm (0.3-0.6 in.) long; the stamens mostly project out from the flower; the ovary is broadly ovoid to obovoid, becoming 3-lobed once it has been pollinated and begins to develop. The berries are reddish orange to bright red, with 6–12(–18) seeds; they are roughly globose in shape and 12–18 mm (0.47-0.71 in.) across. True to its common name, under magnification, the surface of the fruit is distinctly rough and wart-like. (Utech 2002)

Sterile plants can be difficult to tell from Streptopus roseus (rose twisted-stalk) and other Liliaceae (members of the lily family).

  Habitat

In Minnesota, the lone population of P. trachycarpa occurs on a ridge top in a mixed hardwood-conifer forest (northern mesic mixed forest) of Pinus banksiana (jack pine), Populus tremuloides (quaking aspen), and occasional Picea glauca (white spruce), Abies balsamea (balsam fir), and Betula papyrifera (paper birch). Sunlight is direct or, some parts of the day, it is filtered through a rather open tree canopy. Soils are shallow over bedrock. The understory cover of shrubs and saplings range from sparse to moderately dense and include young Abies balsamea, Diervilla lonicera (bush honeysuckle), Lonicera canadensis (fly honeysuckle), Alnus viridis (green alder), Amelanchier sp. (juneberry), and Acer spicatum (mountain maple). Associated forbs include Moerhingia macrophylla (large-leaved sandwort), Maianthemum canadense (Canada mayflower), Cornus canadensis (bunchberry), Aralia nudicaulis (wild sarsaparilla), and Linnaea borealis (twinflower) (Gerdes 2013).

Elsewhere in its range, P. trachycarpa occurs on wooded slopes, often near streams (Hitchcock and Cronquist 1974), and dry-mesic to xeric basaltic ridge tops in Picea glauca /glade ecotones (Judziewicz et al. 1997).

  Biology / Life History

Prosartes trachycarpa is a herbaceous perennial species in the lily family (Utech 2002). The flowers are of the type typically pollinated by any number of flying insects that seek nectar or pollen from flowering plants.

The fruit is a brightly colored berry, with 6-12 seeds. It is likely that the fruit would be attractive to any fructiferous animal that might eat the fruit then, sometime later, pass viable seeds through its digestive system, thereby dispersing the seeds. Although there has been no research reported in the scientific literature confirming this, it seems a reasonable assumption.

  Conservation / Management

The nearest site of P. trachycarpa outside Minnesota occurs on Isle Royale, Michigan, where it is listed as threatened. It has been suggested that the Michigan plants face few threats other than excessive foot traffic (Michigan Natural Features Inventory 2007). A preliminary assessment of the Minnesota population of P. trachycarpa could reasonably come to the same conclusion.

Activities as seemingly benign as hiking must be considered serious threats and routed away from the habitat. Even scientists who visit the site for legitimate purposes must be very careful not to disturb the ground while walking through the habitat. It may also be necessary to respond to the successional changes of the vegetation that appear to be negatively impacting habitat suitability. This may involve careful removal of selected trees or shrubs.

  Best Time to Search

In Minnesota, P. trachycarpa flowers around mid-May. The fruits, strikingly reddish-orange in color, have been observed remaining on the plants in mid-August. Therefore, it is recommended that searches be conducted from mid-May to mid-August.

  Authors/Revisions

Welby Smith (MNDNR), 2018

(Note: all content ©MNDNR)

  References and Additional Information

Gerdes, L. B. 2001. A contribution to the flora of the Rove Slate Bedrock Complex Landtype Association, northern Cook County, Minnesota, U.S.A. Thesis, Michigan Technological University, Houghton. 79 pp.

Gerdes, L. B. 2013. Fairy bells (Disporum trachycarpum). Species new to Minnesota: rough-fruited fairy bells. Minnesota Biological Survey, Minnesota Department of Natural Resources. <http://www.dnr.state.mn.us/wildflowers/fairybells.html>. Accessed February 2013.

Hitchcock, C. L., and A. Cronquist. 1973. Flora of the Pacific Northwest: an illustrated manual. University of Washington Press, Seattle, Washington. 730 pp.

Hitchcock, C.L., and A. Cronquist. 1974. Flora of the Pacific Northwest: An illustrated manual. 2nd printing, with corrections. University of Washington Press, Seattle. xix + 730 pp.

Judziewicz, E. J., F. H. Utech, and W. Mackinnon. 1997. Prosartes (Disporum) trachycarpa (Liliaceae) in Isle Royale National Park: new to Michigan and the eastern United States. The Michigan Botanist 36:63-72.

Michigan Natural Features Inventory. 2007. Rare species explorer.<http://mnfi.anr.msu.edu/explorer>. Accessed 11 February 2013.

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.

U.S. Forest Service. 2006. Regional forester sensitive plants. U.S. Forest Service, Eastern Region, Milwaukee, Wisconsin.

U.S. Forest Service. 2008. Superior National Forest Rare Plant Guide [web application]. U.S. Forest Service, Region 9, Superior National Forest, Duluth, Minnesota. Accessed 10 July 2009.

Utech, F. H. 2002. Prosartes. Pages 142-145 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 26. Oxford University Press, New York, New York.