Walton, G.B. 1995. Report for the 1994-1995 status survey for Sparganium glomeratum in Minnesota. Final report submitted to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resources. 48 pp.
1. Sparganium glomeratum (clustered bur reed) is an aquatic emergent plant species with an interruptedly circumboreal distribution that until recently was known from only 8 stations in North America (2 in Canada and 6 in Minnesota). A spate of discoveries of new S. glomeratum populations in Minnesota between 1990 and 1993 prompted questions regarding the species' actual range, distribution, and abundance in the state. In 1994 under a grant from the Minnesota Department of Natural Resources (MDNR) a status survey of S. glomeratum in Minnesota was begun.
2. Three new sites (Peyla, Blackhoof, and Rice Lake Township), 5 new populations (Duluth) and 1 historical site (Twig) were located during the 1994 Status Survey, plus two more colonies in Superior, Wisconsin during work on other rare plant surveys. The 1994 and 1995 Status Survey investigated 112 wetland sites for S. glomeratum in southwestern, southern, and northern St. Louis County, Cass County, Clearwater County, Carlton County, and Lake County. As a result of the 1995 Status Survey S. glomeratum was found at 11 sites 8 of which are reports from new sites. Seven new sites for S. glomeratum were found in St. Louis County, and 1 in Carlton County in 1995. From sites discovered in 1994 1 new colony was found in Duluth, 1 in Rice Lake Township, and 1 in Skelton. After extensive searches during both years of the Status Survey 2 historical sites (Knife River and Minnesota Point) were determined to be extirpated, and 1 was determined to still be extant (Twig). Two other historical sites (Itasca County and Basswood Lake) were not revisited. Two colonies at a recently discovered site in Clearwater County were confirmed end 5 others were found in the same area. Recently discovered sites in Cass County could not be relocated arid no new sites were found in Cass County. During work on other rare plant surveys in Wisconsin 5 new sites were discovered in Douglas and Washburn counties and additional colonies were found in Superior, Wisconsin.
3. S. glomeratum populations were found to be typically small and scattered. The size of any particular population did not seem to be connected to the size of the wetland. Human disturbance to habitat appeared to be detrimental to S. glomeratum in urban areas but less so in rural areas, where it was sometimes found in recently cleared ditches. The number of associated species found with S. glomeratum was 141. Of this number 65 are typically boreal species and many are circumboreal in their distribution. Most are also species of minerotrophic rather than ombrotrophic wetlands. Habitats where S. glomeratum was found shared several common features including shallow water, fine textured organic soils, and associated species of emergent graminoids.