Small White Aster (also Calico Aster?)

Symphyotrichum recemosum (?) (formerly Aster vimeneus)

There is great taxonomic confusion about this plant and various sources provide conflicting scientific and common names. The common name and former scientific name given here follow Peterson, whose description tallies most closely with this specimen.  

Distinctive are the smooth purple stem, numerous small (1/2" or less) white flowers, relatively tall and open habit, narrow leaves (to 6" long), untoothed or near base slightly toothed on edges

2-5 feet, sun to part shade.

Late Summer-Autumn (August-October).

Close-up of leaves and stems, both quite smooth.  

17 September 2020.

Small White Aster, 17 September 2020.