Carex supina ssp. spaniocarpa (Steud.)Hulten
Weak Arctic Sedge
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Carex spaniocarpa, Carex supina
Basis for Listing
Carex supina ssp. spaniocarpa (weak arctic sedge) is primarily a species of low arctic habitats, principally non-calcareous ridges, cliffs, and outcrops. It has been found at only two locations in Minnesota, both in Cook County (Border Lakes Subsection). The first was discovered in 1889 on a cliff on the south side of South Fowl Lake. The second was found in 1936 at the foot of a cliff on the south side of Clearwater Lake. Both of the sites have been searched recently, but only the South Fowl Lake population has been rediscovered. Still, potential habitat is extensive and very difficult to search; and the species is small and inconspicuous so there is hope that additional populations may await discovery.
Carex supina ssp. spaniocarpa was listed as special concern in Minnesota in 1996. At that time, it had not been seen in the state for 60 years and was feared extirpated. It was rediscovered at South Fowl Lake in 2009, confirming the species still occurred here. For that reason, its status was changed to endangered in 2013.
The stems of C. supina ssp. spaniocarpa grow to about 30 cm (12 in.) tall and are loosely clumped. The leaf blades are 3-15 cm (1.2-5.9 in.) long and 1.0-1.5 mm (0.04-0.06 in.) wide. There is usually a long superficial rhizome. The flowering spikes are 5-15 mm (0.2-0.6 in.) long, with reddish purple floral scales. The perigynia are yellow with dark reddish purple beaks and are 2.5-3.3 mm (0.10-0.13 in.) long (Ball and Murray 2002).
It is rare that perigynia have distinctive colors, but the perigynia of C. supina ssp. spaniocarpa are striking canary-yellow tipped, with dark reddish purple beaks, a color pattern unique among the sedges of Minnesota. The scales are also prominently reddish purple as are the base of the bracts. The perigynia and scales would be striking if they were not so tiny. A mature specimen should be unmistakable if a close inspection is made of the perigynia.
Carex supina ssp. spaniocarpa occurs on partially shaded, dry-mesic to mesic shelves and ledges on north- to west-facing cliffs in the Rove-Slates Bedrock Formation. The cliffs are up to 50 m (164 ft.) tall, with sheer faces. The Minnesota population occurs on a mid-cliff setting on the south side of a deep, cold lake; while an Ontario population on the north side of the lake occurs in a narrow band of open habitat at the top of the cliff. Though similar microhabitats are present on a number of the larger cliffs of this border region, Carex supina ssp. spaniocarpa appears to be restricted to only a very few of them.
Biology / Life History
Carex supina ssp. spaniocarpa is a perennial that can produce long rhizomes. The rhizomes serve the function of vegetative reproduction. They allow plants to spread, forming loose colonies along the narrow ledges, and they also may help hold the plants securely in somewhat unstable substrate.
Conservation / Management
The habitat at Clearwater Lake occurs in the Boundary Waters Canoe Area Wilderness (BWCAW) and is apparently secure from human disturbance. However, it must be stated that the species has not been seen there since 1936. Although it is uncertain whether the species still occurs there, a considerable amount of inaccessible cliff habitat has yet to be searched.
The site at South Fowl Lake is just outside the BWCAW boundary, and logging operations have occurred on state land nearby. It is uncertain what affect logging would have on the cliff habitat, but increased erosion is a possibility. Recreational rock climbing on the sensitive cliff faces could potentially pose a threat to both populations.
Best Time to Search
The best time to search for C. supina ssp. spaniocarpa in Minnesota is when mature perigynia are present, from early June through July.
Welby Smith, MN DNR, 1988, 2008, and 2018
Ball, P. W., and D. F. Murray. 2002. Carex sect. Lamprochlaenae. Pages 556-557 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York, New York.
Butters, F. K., and E. C. Abbe. 1953. A floristic study of Cook County, northeastern Minnesota. Rhodora 55:21-201.
Coffin, B., and L. Pfannmuller, editors. 1988. Minnesota's endangered flora and fauna. University of Minnesota Press, Minneapolis. 473 pp.
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, Michigan. 79 pp.
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.
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.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis, Minnesota. 320 pp.