Slender rush

Species new to Minnesota

by Lynden Gerdes, MBS Botanist/Ecologist

Slender rush (Juncus subtilis E. Meyer) - First vouchered from Minnesota in 1998 from northern Cook County.

a pressed specimen of J.subtilis
Slender rush (Juncus subtilis) August 11, 1998. Photo by Lynden B. Gerdes. larger image(130kb)

location of slender rush
Location of Slender rush in Minnesota

This small rush primarily occurs in the northeastern United States and in Canada; occurring from Greenland to Maine and west to Ontario. It is known to occur in the Thunder Bay District of Ontario, including the Ontario and Minnesota border lakes region (Brunton 1987). According to Oldham (2000), this species is quite widespread in Ontario (15 records on file) ranging from the Ottawa River (Ottawa northward to about the Chalk River) in southern Ontario; north to several sites in the Hudson Bay Lowlands near James and Hudson Bays; and west to four sites in Thunder Bay District.


Across its range, this obscure, slender emergent rush is known to occur on sandy, gravelly and muddy shores. In Minnesota, the lone population occurs lakeshore in shallow water, where it sometimes becomes a stranded emergent on a gently sloping, sandy-bottomed bay. The small, prostrate plants have septate leaves and six stamens. Associated species include: least spike-rush (Eleocharis acicularis). The plant's small size and possible sporadic occurrence due to fluctuating water levels may result in this species being considerably overlooked (Oldham 2000).

Recommendations for additional searches and survey in northern Minnesota include: shallow water and sandy/gravel shores of lakes and interconnecting streams; late July to early September; take advantage of drier years or periods having lower water levels.

Status in Minnesota
Only one location is known for this species in the state. This new addition to our state flora is currently 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.

Brunton D.F. 1987. A Reconnaissance Life Science Inventory of La Verendrye Waterway Provincial Park, Thunder Bay District, Ontario. Prepared for Canada Heritage Rivers System - Environment Canada and the Parks Branch -Ontario Ministry of Natural Resources. 114 pp.

Flora of North America Editorial Committee. 2000. Flora of North America. Vol. 22. Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford University Press, New York. 352 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.

Gleason, H.A., and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Canada. 2nd ed. The New York Botanical Garden. Bronx, NY. 910 pp.

Oldham, M. J. 2000. Personal correspondence. Natural Heritage Information Centre. Ontario Ministry of Natural Resources, Peterborough, Ontario.

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