Summer annual, 0.2-2.5 m tall, found throughout the United States, producing abundant pollen that is a primary cause of hay fever.
There are 17 species of ragweed in North America.
Ambrosia is the generic name of ragweed and in the Latin means "food of the gods."
Ragweed grows the best in sunny, newly-disturbed soils, free from competition with other weeds and grasses. It is often found along roadsides, vacant lots, river banks, and abandoned fields.
Ragweed starts blooming in the north about mid-August as the days become shorter and the nights longer. Pollen production ends mid-September as temperatures start dropping below 60 °F.
It is estimated that one ragweed plant can produce
up to 1 billion pollen grains.