Geocarpon groenlandicum

About

Geocarpon groenlandicum, the Greenland stitchwort or mountain stitchwort, Appalachian stitchwort, mountain sandwort, smooth mountain sandwort, and smooth sandwort is a rare perennial which grows low to the ground in clumps linked together at the bottom. It has three to five pairs of leaves in a linear opposite pattern along the length of the slender stem. The main stem breaks into one to thirty cymes which each flower separately. The flowers are white and arise five to ten centimeters above the thick foliage. The white flower petals are six to ten millimeters long. The petals are, in turn, surrounded by five green sepals.

Summary from Wikipedia