Smelowskia borealis is a unique and distinctive alpine herb in the mustard family (Brassicaceae) that is endemic to the mountains of Alaska and Yukon Territory. This species grows almost exclusively in open, loose alpine scree slopes in Denali. Smelowskia borealis has drooping stems bearing many pink-purple flowers. Plants are densely short-hairy, growing from a long woody taproot, which can is pliable allowing it to stretch (not break) as rocks shift and move downhill in its geomorphically-active habitat. The plant has a fuzzy, circular basal rosette of leaves often surrounded by withered leaves of previous years at the base of the stem. Leaves are oblong to wedge-shaped with a 3-lobed tip (sometime more lobes), grayish-green and pubescent. Stem leaves are similar, but smaller and without petioles. Plants have multiple decumbent flowering stems, 6-30 cm long (longest in fruit), but lying on the ground. Each flowering stem bears a raceme of 20-40 flowers. As with all mustard family plants, there are 4 sepals, 4 petals, and 6 stamens. Sepals are persistent and purplish, and petals are larger than sepals, and pink-purple. The fruits are obovate to ovatesiliques, 8-10 mm long. No other plants in Denali are densely wooly, with several flattened stems bearing clusters of pink-purple flowers.
Smelowskia borealis is perennial and usually begins flowering in early summer (late-May- early-June) and flowering stems continue elongating and flowering through June.
S. borealis is monoecious and insect pollinated. Fruit are dehiscent but seeds have no special dispersal adaptations and are likely gravity disseminated.
S. borealis is endemic to the high mountains of Alaska, Yukon Territory, and extreme western Northwest Territory. In Alaska, S. borealis occurs in the central and eastern Alaska Range and Brooks Range. In Denali this species occurs occasionally in suitable scree habitat in the mountains on both sides of the Alaska Range.
S. borealis is an alpine plant that is found growing in the park at elevations from 853 m to 1787 m with an average site elevation of 1319 m. This species strongly prefers steep slopes with an average slope angle of 26 degrees. It is more commonly found on south-facing aspects.
S. borealis grows on calcareous loose scree slopes and gravelly alpine tundra. The tough long taproot of S. borealis anchors the rosette and flowering stems allowing them to 'float' on top of the unstable scree where it grows. S. borealis is a strong calciphile and was only found on growing in a very narrow range of soil pH: 7.4 to 7.5, with an average pH of 7.45.