Carex formosa Dewey
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Basis for Listing
Carex formosa has a very restricted and disjunct range and is considered rare or local in most of the states and provinces where it occurs. In Minnesota, it is known by historical records to have occurred at four locations in the Twin Cities metropolitan area, all of which date prior to 1938. After repeated unsuccessful attempts to rediscover these populations, it appears that all of these sites have succumbed to urban development. Only recently have a handful of extant populations been located in southeastern Minnesota; these are quite separate from the known historic populations in the state and populations in Wisconsin and North Dakota (Wheeler 1983). The extant populations occur in wooded ravines and river valleys; fragile habitats that cannot sustain heavy use. Because these habitats are also prime locations for residential development, timber harvest, and livestock grazing, the few remaining populations are particularly vulnerable. Given its extreme rarity and vulnerability, C. formosa was listed as an endangered species in Minnesota in 1996.
Sedges are grass-like, perennial plants that can be easily identified to the genus Carex by their three-ranked leaves, closed sheaths, and triangular (only occasionally round), mostly solid stems, with terminal inflorescence. However, identifying a sedge to species is often difficult and positive identification usually requires mature perigynia (the structure that appears to be the seed or fruit but is actually a bract enclosing the ovary) to be present. The fruit enclosed by the perigynium is an achene (Gleason and Cronquist 1991). Carex formosa can sometimes be confused with the very rare Carex davisii (Davis' sedge). Both species have terminal spikes with male and female flowers. Leaves of both species are pubescent (hairy), at least on the underside, and leaf sheaths are strongly reddened at the base. Carex formosa can be distinguished by its lateral spikes, which have both male and female flowers. Lateral spikes of C. davisii have only female flowers. Furthermore, scales of C. formosa are short-pointed and much smaller than the perigynia.
In Minnesota, the historic populations of C. formosa are known from moist areas in deciduous woodlands along the Mississippi River (Wheeler 1981). The extant populations in southeastern Minnesota are in forests on low river valley slopes dominated by Acer saccharum (sugar maple), Quercus macrocarpa (bur oak), Tilia americana (basswood), and Ulmus americana (American elm). Although extremely rare, C. formosa may be locally abundant.
Biology / Life History
Carex formosa is a perennial that reproduces only by seeds. Flowers are wind-pollinated, and dispersal mechanisms are unknown.
Conservation / Management
It is presumed that all of the historical occurrences of this rare plant are gone. The few extant populations located in southeastern Minnesota are found primarily in wooded ravines and river valleys with the right combination of light, temperature, and moisture. This habitat type is particularly vulnerable to housing developments and other land conversion activities on either the slopes themselves, or on level land above the slopes, which could lead to erosion and indirect changes to the habitat of C. formosa. Invasion of non-native species, such as Rhamnus cathartica (common buckthorn) and Alliaria petiolata (garlic mustard), is a serious threat. Any habitat changes that alter the specific light, temperature, and moisture regime would almost certainly be harmful to C. formosa. Timber harvest and livestock grazing in particular are potentially serious threats.
Conservation Efforts in Minnesota
One site of C. formosa occurs in a county park, but management plans that address the ecological needs of this rare plant are needed.
Ball, P. W., and A. A. Reznicek. 2002. Carex. Pages 254-572 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York.
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. 1988. Natural Communities and Rare Species of Olmsted County. Biological Report No. 51. Minnesota Department of Natural Resources, St. Paul.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis, Minnesota. 320 pp.
Wheeler, G. A. 1981. A study of the genus Carex in Minnesota. Dissertation, University of Minnesota, St. Paul, Minnesota. 501 pp.
Wheeler, G. A. 1983. Carex formosa in North Dakota. The Michigan Botanist 22:162.
Wisconsin Department of Natural Resources, Bureau of Endangered Resources. 1993. Guide to Wisconsin's Endangered and Threatened Plants. Wisconsin Department of Natural Resources PUBL-ER-067, Madison, Wisconsin. 128 pp.