The plant Helenium amarum (yellow sneezeweed).
Any plant in the genus Ambrosia, especially Ambrosia artemisiifolia (common ragweed).
Parthenium hysterophorus (false ragweed)
Picris rhagadioloides (syn. Picris sprengeriana; tall oxtongue)
Artemisia tripartita subsp. tripartita (syn. Artemisia trifida; threetip sagebrush)
Tetraneuris spp.