Cardamine purpurea is a caespitose perennial herb in the mustard family (Brassicaceae) with shiny, lyrate basal leaves and pubescent stems and pedicels. Plants are commonly found in moist areas on rocky slopes, meadows, and alpine tundra, growing up to 12 cm tall from a long rhizome. Leaves are mostly basal, lyrate-pinnate (the terminal segment much larger than the lower segments), spatulate or obovate in outline, pubescent and with entire margins. There are only 1-3 compound stem leaves, similar to the basal leaves, or occasionally simple. The stems are unbranched, and pubescent. The flowers are in a raceme, with ascending pedicels, and have four pink to purple (rarely white) clawed petals, 5-8 mm long. The fruits are linearsiliques and up to 20 mm long. This species is distinguished from others in the genus by the low-growing, caespitose habit, lyrate basal leaves, and pubescent stem and leaves.
Purple bittercress flowers from June through August.
Plants are monoecious with bisexual flowers. Flowers are insect-pollinated. Seed capsules split open to disperse seeds by gravity and wind.
Purple bittercress is an amphi-Beringian endemic species. This species was described from St. Lawrence Island (in the northern Bering Sea, Alaska), occurs on Wrangel Island (in the Chukchi Sea, Russian Far East), throughout arctic and alpine central Alaska, and into the mountains of the Yukon Territory. In Denali, this species occurs primarily in the mountains north of Alaska Range crest, except for stations in the upper Yentna and Chulitna river drainages to the south.
Throughout its range in North American, purple bittercress grows at 600-1800 m elevation (Flora of North America). In Denali it occurs at 383-1753 m, an average of 1172 m, and within a narrower altitudinal range (763-1533 m) on south-facing slopes than on north-facing slopes (383-1752 m). It occurs on inclines over 5 degrees more frequently (87% of occurrences), ranging from 1-36 degrees, and at a moderate average incline (16 degrees) for both aspect classes.