Carex vaginata is a small stoloniferous perennial sedge that occurs widely in Denali in boreal woods and meadows, through shrub tundra, and into the lower alpine zone on both sides of the Alaska Range crest. Carex vaginata is a frequent member of riparian plant communities, and occurs in numerous habitats. This species has bicolored flowers, and stiff, smooth stems that grow to be 15-20 cm tall, growing from scaly stolons. Leaves are basal, much shorter than stem, flat, yellowish green and 1-4 mm wide. The lowest bract is shorter than the inflorescence and distinctly sheathed. Male and female flowers are produced on separate spikes. The inflorescence typically consists of 1-3 spikes. The terminal spike is erect and staminate. Lateral spikes (1-2) are pistillate and usually quite separated from terminal spike. Pistillate scales are shorter than the perigynia, light brown with a broad green midrib. Perigynia are light green, smooth, beaked with 3 stigmas. Fruits are achenes. The uncommon Carex livida is similar, but that plant is taller, the leaves are a glaucous green and the perigynia are unbeaked, and it occurs in much wetter sites than is typical for C. vaginata.
Carex vaginata flowers in early summer in Denali.
Carex vaginata 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 wind and water dispersed. C. vaginata also reproduces readily through stoloniferous growth.
Carex vaginata has a widespread, circumpolar distribution. In North America, Carex vaginata occurs throughout Alaska and Canada and ranges southward into the Great Lakes region and New England states. Carex vaginata is widespread across Alaska, except absent in the Aleutians and southeast panhandle. In Denali, C. vaginata is widespread and common, and occurs on both sides of the Alaska Range crest.
Carex vaginata is a lowland species, occurring from 155 m to 1253 m with an average plot slope of 669 m. It prefers flat to low angled sites with an average plot slope of 6 degrees. It prefers east or west facing plots.