E. smallii of Michigan Flora.

In almost all kinds of wet places; especially common in shallow water of marshes and along marshy shores and river margins; also in bogs, wet meadows, swamp borders, etc.

Plants with slender culms and small achenes are rather easily confused with E. erythropoda, but large robust plants are easily recognized. The summits of the leaf sheaths in E. palustris tend to be blacker than the merely darkened ones of E. erythropoda. The tubercle ranges from dome-shaped (no longer than broad) to elongate in both species, though tending to be shorter and more conical in E. erythropoda. The circumpolar E. mamillata could well occur in the Lake Superior region. It has perianth bristles mostly 5–6 (–8) and averaging longer than achenes (tubercles included); E. palustris has perianth bristles absent or up to 4 (–5) and usually shorter than achene plus tubercle.