by Lynden Gerdes, MBS Botanist/Ecologist
Ross's sedge (Carex rossii F. Boott) - This sedge was last documented in the State during the late 1800s from Carlton and Pine Counties until it was recently discovered on a high cliff top in northern Cook County in 1999. This species is typical of the cordilleran regions of western North America and extends eastward to the northern plains of Saskatchewan and Manitoba. It is also known to occur in the Keweenaw Peninsula of Michigan and in Ontario, Canada. This small, grass like plant is seemingly quite rare in the Upper Great Lakes region.
This species was found during a floristic investigation in northern Cook County, MN as part of a graduate study (Gerdes 2001) receiving support from Michigan Technological University, the Superior National Forest, and the Minnesota County Biological Survey. During this two-year field investigation, three populations of Ross's sedge were recorded from dry, sunny cracks and shallow soils of cliffs and cliff tops. MBS staff has documented two additional locations of this sedge since 1999 while conducting floristic investigations in the North Shore Highlands Subsection. In Lake County the sedge was found growing on a steep, diabase slope in shallow soil and talus. A new location for Ross's sedge has also been documented in Carlton County. Across its range, this sedge also occurs in moist or dry, sandy or rocky, montane woodlands, deciduous wooded slopes, sagebrush slopes, alpine meadows, and prairies (FNA 2002).
In northern Minnesota, where Ross's sedge is known to occur, Carex are best searched for in a period from late May to late July. Sedges occurring in sunny, dry-parched habitats typically flower and fruit early in the season, while species in wetlands and cool habitats are often in their prime later in the season. Aspect, temperature and moisture conditions also influence flower and fruiting times. Survey suggestions for Ross's sedge include searching an assortment of dry, rocky habitats including outcrops, cliffs, talus, and forested slopes during late May to early July. These habitats have a tendency to warm up early in the season with many sedges flowering, setting and dropping their achenes by mid-late June and early July. This species is quite easily confused with several other species in Carex section Acrocystis (Montanae) (i.e., Carex deflexa, C. umbellata, and C. tonsa). Since this species shares similar growth forms and habitats with the more common sedges in this group, successful field efforts may demand considerable effort and observation time. Specimens having mature fruits are critical for accurate identification. Illustrations of the sedge can be found by clicking here.
None of the historic populations of Ross's sedge have been relocated. At this time, five populations are known to occur in Minnesota.
Status in Minnesota
Ross's sedge is currently not a listed species in the State but the MN-Natural Heritage Program is tracking its distribution. Due to recent discoveries of this sedge in Minnesota, the species is undergoing review for potential listing as Minnesota Endangered, Threatened, or Special Concern.
If you are so fortunate to encounter this species during one of your botanical treks, please record its location and contact the Natural Heritage Program for additional information.
Flora of North America Editorial Committee. 2002. Flora of North America. Vol. 23. Magnoliophyta: Commelinidae (in part): Cyperaceae. Oxford University Press, New York. 608 pp.
Gerdes, L. B. 2001. A Contribution to the Flora of the Rove Slate Bedrock Complex Landtype Association, Northern Cook County, Minnesota, USA. (Unpublished Graduate Report - Michigan Technological University, Houghton, MI.) 78pp.
Voss, E. G. 1972. Michigan Flora Part I Gymnosperms and Monocots. Cranbrook Inst. Sci. Bull. 55 and Univ. of Michigan Herbarium. 488 pp.