Rare Species Guide

  Basis for Listing

Carex rossii (Ross’ sedge) was first found in Minnesota in 1896 at an unknown location in Carlton County. In spite of intensive searches, it was not found again until 1999, at a site in Cook County. Since then, only three additional sites have been found. Not only are there very few populations of C. rossii in Minnesota, but the populations are small and consist of few individuals. The limiting factor is the specialized habitat of this species, specifically south- and southeast-facing cliffs, talus slopes, and rocky ridge tops. Although these rocky habitats seem permanent and indestructible, the highly specialized plants that occur there (such as Carex rossii) and their micro-habitats may be vulnerable. Recreational rock climbing, logging on adjacent lands, and construction of recreational trails have been identified as potential threats.

Across its entire range in North America, C. rossii occurs primarily in western and northern regions, especially at high elevation in mountainous areas, where it is found in dry grasslands, open woods, and meadows. In the Midwest, there are small disjunct populations in Minnesota and Michigan (Voss 1972; Coffin and Pfannmuller 1988). Populations in Ontario are also rare and disjunct and are primarily associated with Lake Superior habitats (Meades et al. 2004).

Given the small number of documented populations despite targeted botanical surveys, the species’ unique habitat requirements and limited geographic range in the state, and the vulnerability of the known populations to degradation or destruction, C. rossi was listed as threatened in 2013.

  Description

Carex rossii is a small sedge, with tufts of culms 3-15 cm (1-6 in.) long; the bases of the culms (remnants of old leaf sheaths) are reddish, reddish brown or maroon and somewhat fibrous; the rhizomes grow to about 5 cm (2 in.) in length, are coarse and stout; the leaves are up to 2.5 mm (0.1 in.) wide and usually exceed the culm in length; the terminal spike is staminate and 4.0-8.0 mm (0.16-0.32 in.) long; the lateral spikes are pistillate, with 1-4 per culm; basal spikes are short and nearly hidden among the leaf bases; the bract of the lowest (non-basal) pistillate spike is leaf-like and usually equals or exceeds the inflorescence; the pistillate scales are acute or short-awned, they about equal the perigynia in length or are somewhat longer; the perigynia are moderately to sparsely hairy towards the distal end, are 2.5-4.0 mm (0.1-0.16 in.) long, and 1.2-1.5 mm (0.05-0.06 in.) wide, with a beak 0.7-1.7 mm (0.03-0.07 in.) long, and a stipe 0.3-0.8 mm (0.01-0.03 in.) long (Crins and Rettig 2002).

Carex rossii is most similar to C. deflexa (northern sedge), but the pistillate scales of C. rossii are about equal in length to the perigynia, not significantly shorter. Also be aware that C. umbellata (parasol sedge) is similar and will likely occur nearby, but the bract of the lowest pistillate spike of C. umbellata is awn-like, not leaf-like, and is shorter than the inflorescence. Be prepared to make a close inspection of any suspected C. rossii, and take advantage of any Carex (sedge) expert that might be available. Also know that determination of poor specimens can be difficult, even for an expert.

  Habitat

In Minnesota, C. rossii occurs on south- and southeast-facing cliffs, talus slopes, and rocky ridge tops in the northeastern part of the state (Border Lakes and North Shore Highlands subsections). These habitats are typically exposed to direct sunlight, though they may be shaded for some portion of the day. Soil, if there is any, typically consists of gravel or broken fragments of rock, maybe with some amount of smaller wind-blown particles that have become trapped in a crevice. These habitats tend to dry-out quickly on hot and dry summer days, especially when rainfall is below normal, so they are usually sparsely vegetated. Lichens are the dominant life form in these habitats and likely play an important role in maintaining the integrity of the habitat. However, there is little understanding of how the various biotic and abiotic forces interact. 

  Biology / Life History

Carex rossii is a perennial wind-pollinated sedge. The seeds (achenes) have no specialized dispersal mechanisms and are likely moved about by small animals and, to some extent, gravity. The seeds of most Carex species germinate the year after they are produced, though some seeds of C. rossii are reported to maintain long-term viability in a buried seed bank (Anderson 2008). Carex rossii also reproduces asexually by the growth of rhizomes, which can reach a length of about 5 cm (2 in.) and produce new plants at the nodes. It has been reported that C. rossii in grassland and forest habitats survives wildfire (Anderson 2008). The Minnesota habitats of C. rossii are not particularly fire-prone because of a lack of fuel. They are, however, prone to desiccation during times of below-normal rainfall, since the thin and coarse soils of its habitat cannot hold water for long. Winter conditions must be especially severe, since cliff habitats are more likely to be free of insulating snow than would be a forest habitat. The small stature and narrow leaves of C. rossii are probably adaptive features that enable it to compete under such extreme conditions.

  Conservation / Management

Currently the habitats of C. rossii are not being heavily impacted. Mining activities could impact this species if initiated in the area where this species occurs. Forestry activities do not seem to be a major threat, primarily because merchantable trees are not abundant in C. rossii habitat. However, logging upslope of this species' habitat could impact this species. Recreational activities such as rock climbing could also pose a threat, though it is not known to have happened in Minnesota.

The normal cracking, sloughing, and erosion of rock that occurs in cliff habitats is not considered a threat to populations of C. rossii. The process is continual and inevitable and happens so slowly that populations of C. rossii have ample opportunities to recover before the next rock fall.

  Best Time to Search

Searches for C. rossii are best timed to coincide with the maturation of the reproductive structures, which will make identification easier. In a typical year this occurs from late May to mid-June.

  Authors/Revisions

Welby Smith (MNDNR), 2018

(Note: all content ©MNDNR)

  References and Additional Information

Anderson, M. D. 2008. Carex rossii. USDA, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer) in Fire effects information system [online]. <http://www.feis-crs.org/beta/>. Accessed 18 January 2013.

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, New York.

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

Crins, W. J., and J. H. Rettig. 2002. Carex sect. Montanae. Pages 532-545 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York, New York.

Meades, S. J., D. Schnare, K. Lawrence, and C. Faulkner. 2004. Northern Ontario plant database. Version 1. Algoma University College and Great Lakes Forestry Centre, Sault Ste. Marie, Ontrio, Canada. <http://www.northernontarioflora.ca>. Accessed 01 January 2004.

Michigan Natural Features Inventory. 2007. Rare Species Explorer [web application]. Michigan Natural Features Inventory, Lansing, Michigan.

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.

Smith, W. R. 2018. Sedges and rushes of Minnesota: the complete guide to species identification. University of Minnesota Press, Minneapolis. 696 pp.

Voss, E. G. 1972. Michigan Flora: Part I Gymnosperms and Monocots. Cranbrook Institute of Science Book 55, Bloomfield Hills, Michigan. 488 pp.