Carex obtusata is a rhizomatous perennial sedge with a small, solitary spike, found in warm, dry places in the mountains, including turfy sites in sloping meadows and tundra, mostly in continental climate region north of the Alaska Range crest in Denali. Plants have several 10-20 cm tall stems per reddish-purple rhizome. Leaves are basal, about 1 mm wide with purplish sheathes. Stems lack a bract below the inflorescence. This species has male and female flowers in the same terminal, solitary spike. The staminate flowers are produced above the pistillate flowers. Pistillate scales are acute, brownish with transparent margins, enclosing the perigynia. The perigynia are dark brown, obovate, and slightly two-beaked. The fruits are achenes with 3 stigmas. This species is similar to C. rupestris, but that species is shorter, the rhizome is brown (not purplish) and the perigynia are a dull yellowish-brown, not shiny dark brown.
Carex obtusata flowers in early summer in Denali.
Carex obtusata is monoecious, but with separate male and female flowers in the same spike. Species in the genus Carex are wind pollinated, but usually also self-pollinate to some degree (Bertin 2007; Friedman and Barrett 2009). Seeds are disseminated by wind or gravity.
Carex obtusata is an amphi-Beringian species with an arctic-alpine distribution. In North America, this small sedge ranges from Alaska into western and central Canada and south along the Rocky Mountains to New Mexico. It is also found in the prairies of Minnesota and the Dakotas. Carex obtusata occurs primarily in eastern and northern interior Alaska, quite common in dry bluffs along the Yukon River and its tributaries. In Denali, this species occurs on both sides of the Alaska Range but most commonly on the north side.
Carex obtusata is not common in Denali but found from 631 m to 1406 m, with an average plot elevation of 1104 m. This species prefers steep south facing slopes and the average plot slope is 22 degrees.