Carex bigelowii is an abundant, highly variable, perennial sedge that exhibits different growth forms in different habitats. Plants are found from the lowland to alpine zone in Denali, usually in poorly drained sites on acidic, peaty soil such as bogs, muskeg and tussock tundra. Carex bigelowii can be either caespitose (sometimes forming large tussocks in the lowlands) or rhizomatous and has sharply angled, stiff, scabrous stems 10-40 cm tall. Leaves are mostly basal, flat to revolute and 1.5-4 mm wide. The lowest bract is scale- or leaf-like and shorter than the inflorescence. Plants have male and female flowers in separate spikes, but closely clustered together. Spikes are erect, with usually a single terminal staminatespike and 2-3 lateral pistillatespikes. The pistillate scales are purplish-black to black, equal or shorter than the perigynia and with a blunt or ovate tip, but no awn. Perigynia are green, spotted purple-black or mottled on upper half and with a short beak. Fruits are achenes, elliptic and flattened. Carex microchaeta is superficially similar, but has three stigmas (not two), the pistillatespikes are often peduncled and nodding, and the scales are acute-tipped.
Carex bigelowii is perennial and usually one of the first sedges to flower in the spring in Denali.
Carex bigelowii is monoecious, but male and female flowers are produced in separate spikes. Species in the genus Carex are wind pollinated, but usually also self-pollinate to some degree (Bertin 2007; Friedman and Barrett 2009). Seeds are reportedly still viable after up to 200 years in the soil. This species primarily reproduces vegetatively through spreading rhizomes.
Carex bigelowii is an important food for sheep and caribou.
Carex bigelowii is a widespread circumpolar species. In North America, this sedge occurs from Alaska across Canada to New England, and in the northern Rocky Mountains. It is one of the most common and abundant sedges in Alaska, occurring statewide except for the southern coastal areas. In Denali Carex bigelowii is a common and locally abundant species, occurring frequently, particularly in areas influenced by permafrost.
Carex bigelowii occurs in Denali from 156 to 1533 m, with an average plot elevation of 690 m. It seems to favor north facing over south facing slopes. It favors sites with low slope angles with an average plot slope of 6.6 degrees.