Eriophorum vaginatum
 
Sheathed Cottongrass

Several Shoots

Greenbush Bog, 20 km West of Hudson Bay, SK on Highway #3
30-May-2017

The plant commonly grows in large tussocks and the shoots in the above photo were taken from one of these tussocks.  Note each culm contains a single spikelet.

I had originally identified this species as Eriophorum brachyantherum.  The correct identification was provided by Anna Leighton and I very much appreciate her doing this.  Anna is currently working on the next fascicle that will be published by the Flora of Saskatchewan Association.  That publication (Rushes, Bulrushes and Pondweeds, plus the remaining Monocots of Saskatchewan by Vern Harms, Anna Leighton and Mary Vetter) will cover Eriophorum.