Which ragweed species are major causes of hay fever?
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Asteraceae
The flowering head of a sunflower (Helianthus annuus) is formed of yellow, petal-like ray flowers and a brown center of minute disk flowers.
In the context of the Asteraceae family, the genus Ambrosia, commonly known as ragweed, is the primary source of hay fever in eastern and middle North America due to the vast amounts of pollen it releases in late summer.12
While many species within the genus produce highly allergenic pollen, the following are identified as major species:
- Common ragweed (Ambrosia artemisiifolia): A widespread annual found across North America.1
- Great, or giant, ragweed (A. trifida): A tall annual native to a broad range of North America, from Quebec to British Columbia and south to Florida and California.1
Both of these species are considered pernicious weeds, and because they are annuals, their impact can be mitigated by mowing them before they shed their pollen. Other species, such as the perennial western ragweed (A. psilostachya), are also common throughout North America.1