The common name comes not from any pollen allergy that hay-fever victims might suffer (for wind-pollination is not characteristic of plants with showy flowers), but from use of the dried, pulverized heads to make a snuff that promotes sneezing.

1. Leaves very numerous, crowded, less than 2 mm broad; stems not winged (may be angled or ridged); annual.

H. amarum

1. Leaves not crowded, broader; stem with green wings the length of the internodes; perennial.

2. Disk corollas with 5 yellow lobes; ray flowers pistillate.

H. autumnale

2. Disk corollas with 4 brown or purple lobes; ray flowers sterile.

H. flexuosum