[Wikipedia] Circumpolar Distribution, Habitat, Variable Morphology & Genetics: It has a circumpolar distribution, occurring throughout the northernmost latitudes of the Northern Hemisphere. It is a perennial herb[3] that grows in a wide variety of habitat types, including tundra and taiga and many areas farther south with subalpine and alpine climates. It is extremely variable in morphology, its form depending on both genetic makeup and environmental conditions. (link added by Mary Ann Machi)