Allergy Information

All species are wind-pollinated and usually produce large amounts of pollen. These plants are from moderately to significantly allergenic.

Genus Details

The composites are members of a large aster family (Asteraceae or Compositae). The composites have flower heads that resemble an individual flower, but the head is actually made up of numerous individual small flowers. These are the “other composites” group that includes pollens not otherwise distinguishable between each other. This group excludes all species in Artemisia or Ambrosia genus. These plants usually pollinate during the summer months.

Pollen Description

Pollen grains are oblate-spheroidal to prolate-spheroidal; the amb triangular, 3-4 lobate and 3-4 colporate. The colpi are short or long and the ora vary within species. The sexine is thick and has long or short spines (spinules).

The pollen grains vary from 15-48 x 16-40 micrometers.

Genus Distribution

The shaded areas on the map indicates where the genus has been observed in the United States.

- Native, observed in a county 

- Introduced, observed in a county 

- Rarely observed