Symphyotrichum lanceolatum (Willd.) G.L.Nesom
Family: Asteraceae
eastern lined aster, lance-leaved panicled aster, panicled aster, white panicle aster
[Aster lanceolatus Willd.]
Symphyotrichum lanceolatum image
from USDA Plants website  
Symphyotrichum lanceolatum image
Aaron_Carlson  
Symphyotrichum lanceolatum image
University of Wisconsin-Stevens Point, Robert W. Freckmann Herbarium (UWSP)  
Etymology: Aster: from the Greek aster, "a star," describing the radiate heads of the flowers
Plants: perennial forb