Silene acaulis

A rare crevice, trough or rock garden treasure.  Flowers twice a year.

Moss Campion or Cushion Pink. This is a lovely tight form from Hokonui Nursery, found surviving in an old, inherited trough. No care, yet it burst into bright fresh green wee leaves from an almost dead looking bundle of thatch. The dead leaves from the previous season persist for years evidently but it helps it form a nice mound in my experience.(so it can possibly be a bit messy in late winter anyway). Pink flowers are borne singly on short stalks and cover the plant all spring and again to some extent on into autumn. 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