Symphyotrichum subulatum

Symphyotrichum subulatum (eastern annual saltmarsh aster or, in Britain and Ireland where it is naturalized, just annual saltmarsh aster) is an annual plant in the sunflower family Asteraceae, native to the eastern US and the Gulf coast to Texas. The species grows primarily in coastal salt marshes, although in the Ozarks it occurs as a non-marine weedy variety.