Silene acaulis

Moss Campion or Cushion Pink. A tough plant, lately inherited in old troughs, no care, yet it has burst into bright fresh green wee leaves from an almost dead looking bundle of patchy stems and thatch, the dead leaves from the previous season persist for years. (so can be a bit messy over winter anyway). Pink flowers are borne singly on short stalks and cover the plant all spring. Easy plant for the rock garden or trough. Excellent drainage. It is found all over the high arctic and tundra as well as the mountains of Eurasia and North America. 

According to Wikipedia, plants in Colorado have been estimated to reach 75 to 100 years in age, and Alaskan plants may reach 300 years. The oldest known moss campion is 350 years old and has a diameter of two feet, in the old money.  Photo inset in Svalbard