Synthyris borealis is a squat, woolly alpine plant, with a dense cluster of blue flowers that open soon after the snow is gone and a rosette of round, lobed fuzzy leaves. Endemic to Alaska and the Yukon, this is a unique, distinctive member of Denali's alpine flora that occurs in dry tundra and gravelly places mostly north of the Alaska Range crest.
Plants grow 5-15 cm tall from a rhizome. Plants have both basal and stem leaves with stiff white hairs, though the stem leaves are hidden by the flowers early in the season. The basal leaves are short-petioled and close to the ground, rounded or reniform and lobed, the divisions toothed. Last year's leaves are often persistent and visible on the ground beneath the new growth. The stem leaves are much smaller, egg- or fan-shaped, toothed at the tips. The stems are thick.
When the plants are in bloom, they are often not much taller than a few centimeters, expanding during fruiting. The inflorescence is a dense spike-like raceme, with wooly bracts in between flowers, almost hiding the petals. The petals are a true blue color. The corolla (fused petals) is bilaterally symmetric and two-lipped, the upper lip is slightly longer and has one notch, and the lower is 2-notched. The two stamens are exerted at the top of the flowers, the style is beneath them. The style and filaments are also blue, the anthers with yellow pollen. Flowers produce heart-shaped capsules, longer than they are wide. The capsules split along the top, releasing circular seeds.
Another alpine plant with a dense spike of bilaterally symmetric blue flowers is Lagotis glauca, but that species is taller, lacks the dense wooliness, and does not have reniform leaves. Also, Lagotis occurs in lush meadow habitats whereas Synthyris occurs in barren, rocky sites or sparse Dryas tundra.
Flowers bloom early, typically late May and early June. Later in the season, the inflorescence elongates.
S. borealis is monoecious with bisexual flowers. The showy blue flowers are likely to attract pollinators. Flowers of other species of Synthyris are both insect-pollinated and self-compatible (McKone et al. 1995). Seeds lack any specialized dispersal adaptations.
Synthyris borealis is an Alaska-Yukon endemic species, also barely reaching Northwest Territory in the Richardson Mountains. In Denali, this species is common across the northern slope of the Alaska Range, and in the northern foothills. There is one locality on the south side of the Alaska Range, near the north fork of the Chulitna River.
This is a genuine alpine species, found from 802 meters to 1787 m, with a mean of 1288 m. It is found on steep slopes (20 degrees incline and above), but shows no preference for aspect. However, the specimens from southern aspects were found on a wider range of elevations.