Calamagrostis lapponica is a tall, loosely tufted perennial grass with narrow panicles, found most commonly in heaths and shrub tundra from uplands into the subalpine zone in Denali (most frequently north of the Alaska Range crest). Plants grow up to 1 m tall from subterranean runners. Leaves are flat, 5-15 cm long, scabrous, and narrow (2-4 mm). Ligules are membranous, 1.5-4 mm long with entire margins. The stem typically only has 2 or 3 nodes. The inflorescence is a loose panicle, 5-15 cm long, 1.5m wide, and sometimes becomes purplish-brown with age. The spikelets have one bisexual flower. Glumes are long (4-5.5 mm) and narrow (at least 3x longer than broad) with an acute tip. Lemmas are slightly shorter than glumes (3.5-5 mm) with a short awn. The characteristic callus hairs are numerous and of equal length to the lemma. The fruit is single-seeded, indehiscent and dry. This plant can be distinguished from other local Calamagrostis species by the long, narrow panicle and the narrow glumes, more than 3 longer than they are broad.
Calamagrostis lapponica greens up in early summer (late May-June) and produces flowers in mid to late summer (July-August).
C. lapponica is monoecious, with stamens and pistils in the same florets (bisexual). Flowers are wind pollinated. Seeds are wind and gravity dispersed. It also readily spreads vegetatively through runners.
Calamagrostis lapponica is a circumpolar species with an arctic-alpine distribution that ranges across northern Eurasia, Alaska, across all Canadian provinces and Greenland to Europe. In Alaska this species occurs occasionally statewide except apparently is absent along the southern coastal areas and in the Yukon-Kuskokwim delta region. In Denali, C. lapponica occurs primarily in the mountains north of the Alaska Range with a few localities in the vicinity of Broad Pass to the south.
C. lapponica is found in the park at elevations from 314 m to 1227 m with an average site elevation of 824 m. It appears to slightly prefer north-facing slopes. It is found on sites with a wide range of slope angles (1-35 degrees) with an average angle of 9 degrees.