Three subspecies have been recognized within Silene repens on the basis of stature and the development of purple pigment in the calyx. Northern populations in the flora area have been referred to subsp. purpurata because of the unusually heavy pigment of the calyx, while the disjunct populations in the central Rocky Mountains have been recognized as subsp. australis. However, both of these forms occur among collections from Eurasia that have been referred to subsp. repens. When material from populations of subsp. purpurata was grown farther south, it took on the appearance of subsp. australis, suggesting that the differences are under environmental influence.