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Photo by: Gary Fewless

Location: Brown Co., WI

Date taken: August 4, 2001

Camera: Olympus CL 2500L digital camera

 

common ragweed.

Common Ragweed (Ambrosia artemisiifolia)

A close-up of Common Ragweed leaf shapes.

Common Ragweed (Ambrosia artemisiifolia), is the most troublesome of the plants causing hayfever in Wisconsin. In fact this species and Giant Ragweed (Ambosia trifida) are believed to be responsible for more pollen-induced hayfever than all other plants combined in the United States. Many people blame the Goldenrods (Solidago spp.) that are blooming at the same time as for their hayfever, but that is seldom the cause. It all has to do with the pollen. Ragweed flowers are are inconspicuous because they depend on the wind to transport pollen from flower to flower. They do not need to invest energy in bright showy flowers like the Goldenrods because they do not need insectsfor pollination. However, in order to have effective wind pollination that pollen must be very small in order to move great distances and this makes it more likely to be inhaled and cause hayfever. Goldenrods depend on insect pollination and their pollen is generally not dispersed significantly by the wind. In fact, as a general rule, plants with showy, conspicuous flowers are usually not important sources of hayfever, even if people are allergic to them, simply because the amount of pollen that is actually carried to people is very small.

Contributed by Gary Fewless

© 2001-2004 The Cofrin Center for Biodiversity and the University of Wisconsin Green Bay, All Rights Reserved
Last updated on April 15, 2014