Siberian aster is a purple-flowered member of the aster family (Asteraceae) that occurs widely in Denali, primarily in floodplains but also frequently in subalpine and alpine meadows and occasionally in open soil in dry tundra. Plants grow up to 50 cm tall from a branched rhizome. The basal leaves are deciduous. The stem leaves are elliptic to oblong, up to 10 cm long, and densely short-hairy on the lower surface with small teeth. The lower stem leaves are usually smaller, the middle ones unstalked. The flowering heads are solitary to many, 6-16 mm tall. The involucralbracts are usually green-tipped and purple-margined. There are 10-25 ray flowers, white to pale violet or purple. The disc flowers are yellow becoming purplish, and the pappus dark cinnamon or reddish tan. Fruits are hairy achenes. Siberian aster is distinguished from other asters in Alaska in having pubescent, purple tipped involucralbracts without glands.
This species flowers mid-summer in Denali.
Eurybia sibirica is monoecious with pistillate and bisexual flowers. Flowers are protandrous—the anthers releasing pollen before stigmas are receptive. Plants can be self-fertilized, but are mostly reliant on insect visitors, predominately butterflies and halictid bees (Armbruster and Mcguire 1991). Seeds have a tuft of hairs which aids in wind dispersal.
Eurybia sibirica is an amphi-Beringian species with a boreal montane distribution. This species occurs in the northern Rocky Mountains (Wyoming, Idaho, Montana, Alberta, British Columbia), the northern Pacific Coast (Oregon, Washington, British Columbia), northwards through the Yukon and Northwest Territories, Alaska, and across the Bering Strait into northern Eurasia to Europe. Eurybia sibirica is common on floodplains and open soil throughout Alaska and occurs more frequently on the north side of the Alaska Range in Denali than to the south.
Arctic aster has the greatest elevational range of the four asters which occur in the park (134-1494 m). However, it occurs most frequently in the upper montane to alpine zones with median occurrences between 900 and 1200 m on both north and south-facing slopes. It had the greatest cover in sample plots in elevations greater than 1100 m. It occurs on inclines up to 47 degrees with the majority of occurrences between 12 and 30 degrees and the greatest coverage in plots with an incline greater than 28 degrees.