Sterile sedge (Carex sterilis) in Minnesota occurs only in wetlands, usually in alkaline rich (calcareous) fens but also in calcareous wet prairies. When it is found it is often the dominant species. However, it is classified as threatened in Minnesota due to continued loss of its preferred habitat.
Sterile sedge forms dense tufts of many plants. The slender, grass-like leaves are up to 10″ or more long, no more than ⅛″ wide, and are folded like a fan. The stems are stiffly erect, triangular in cross section, brown at the base, and up to 29″ long. The inflorescence at the end of the stem has usually four easily distinguished spikes. The inflorescences are highly variable. The terminal spike is usually all male (staminate) or all female (pistillate) but may include some flowers of the opposite sex. Some plants have all staminate spikes, some have all pistillate spikes, and sometimes a few flowers of the opposite sex are scattered on some of the spikes. The common name of the plant refers to the fact that some clumps are all staminate, do not produce seed, and are therefore sterile.
Sterile sedge is similar in appearance to, and easily confused with, interior sedge (Carex interior). The two species often appear at the same site. However, interior sedge is less stiffly erect, has even narrower leaves, and usually has only three spikes per stem. The terminal spike of interior sedge has a narrow, club-shaped, staminate portion at the base that is as long as the broad, star-like, pistillate portion.