Usually in coniferous bogs and swamps, even in dense shade under cedar, spruce, tamarack, fir, and/or hemlock; less often in swampy mixed forests or boggy hollows in sandy soils, generally in acidic soils. 

The perigynia are distinctly plano-convex and the staminate flowers basal in this species, which is sometimes confused with C. disperma, which, however, has plump, biconvex perigynia and male flowers apical in the spikes, See also notes under Carex billingsii.