Diapensia lapponica is a slow growing, long-lived perennial alpine dwarf shrub that forms distinctive compact cushions with showy white flowers. It occurs in tundra and fellfields across Denali. Leaves are tiny, obovate to oblong, leathery, thick and shiny with a revolute margin, borne in circular rosettes. Flowering stems are short and leafless and produce a single flower. Flowers consist of a 5 lobed white or cream colored corolla (fused petals), lobes 7-10 mm, and 5 red-purple sepals. Fruits are brown capsules, 3-4 mm across. This is the only alpine cushion-forming plant with white flowers and leaves with a revolute margin. In fruit, it would be easy to confuse with alpine azalea (Loiseleuria procumbens), which has similar leaves, but that plant often produce multiple flowers/fruits at the top of one stalk and tends to grow in a more matted habit as compared to the cushion-forming Diapensia.
Diapensia lapponica is a perennial cushion plant that has evergreen leaves. It species typically flowers in mid-summer.
This species is monoecious with bisexual flowers. Diapensia lapponica is insect pollinated, primarily by bumblebees, wasps and flies. Flowers are slightly self-compatible, but almost all seeds produced in the wild are the result of insect visits (Molau 1993). This species is slow growing, spreading 0.5-1 cm a year from a central to form large cushions. Individuals can live for hundreds of years (Molau 1997). Plants typically begin flowering after 15 years of growth. There is no evidence of layering or spread via rhizomes.
Diapensia lapponica in the broad sense has a circumpolar distribution. This species is sometimes broken into two species, or subspecies based on growth form and leaf characteristics with the Alaska taxon being called either D. lapponica subsp. obovata or D. obovata. The distribution of D. obovata is amphi-Beringian, including Alaska, Yukon, Northwest Territories and British Columbia in North America and Chukotka, Siberia, and the Russian Far East in Eurasia. This species is widespread in mountainous areas across Alaska except absent in the Aleutians and southeastern panhandle. In Denali, D. lapponica sens. lat. is common in suitable alpine habitat park-wide, on both sides of the Alaska Range crest.
Diapensia lapponica is primarily an alpine species and is observed at elevations from 274 m to 1573 m with an average plot elevation of 1077 m. This species prefers northern and east-west aspects to southern exposures. It is also prefers steeper sites with an average plot slope of 16 degrees.