sneezeweed

Short definition from Wiktionary

Noun

1. 1
   A plant of the genus Helenium, especially Helenium autumnale.
2. 2
   A plant of the genus Centipeda; either of the species Centipeda cunninghami or Centipeda minima, which induce sneezing and are known as a folk remedy for colds and allergic reactions.
3. 3
   Synonym of sneezewort (Achillea ptarmica).