There is a small possibility this could be Carex lupuliformis (which is Critically imperiled in Ontario). A diligent field check would examine the achenes which are rhomboid in C. lupiliformis and broad, somewhat flattened in lupulinus. A quicker method might be to squeeze the head which will feel spiny in the case of C. lupuliformis.
The status of C. lupuliformis means that any occurences of this species in Ontario and other applicable jusidictions should be reported to relevant authorites.