This is Apocynum sibiricum, also known as Clasping Dogbane. The flowers are white, yellow, green, and chartreuse. This plant has been used to make cord and thread for hundreds of years. They attract a wide variety of bees, birds, and butterflies. Apocynum in general are nectar sources for Apple sphinx, Great ash sphinx, and Poecila sphinx moths, and they are a larval host for the Snowberry Clearwing moth. USDA Hardiness Zones 3 to 11.