Marshes and wet hollows, often in shallow water at the edges of ponds and lakes. Rather local even though distributed throughout the State. However, as it may grow in deeper water, frequently 6–9 dm, than any other Carex species, perhaps also overlooked.

Sometimes specimens from deeper water settings will have the pubescence evident only at the summit of some of the leaf sheaths. The vegetative culms of this species are hollow, allowing their easy recognition when fresh, even if pubescence is hard to see. Occasionally, the inner bands of the sheaths may be quite reddend, but vegetative shoots are still easily distinguished from those of Carex trichocarpa, as the reddened portion is not shiny and thickened, usually pubescent apically, and with veins clearly visible (and sometimes breaking into fibres). 

Hybrids with C. trichocarpa are suspected from Monroe Co.