The ragweed is a Compositae and is one of the most important allergen's of North America. They produce copious amounts of pollen and are wind-pollinated. They are especially predominant in the northeastern part of Canada from Manitoba to Nova Scotia. In the United States the predominance is in the Midwest and Northeastern States. The pollination season starts in July and ends in November (December in some States). All species are considered highly allergenic and there is a high degree of cross-allergenicity between species. Many of the Compositae share the same allergens as ragweed. The Compositae grow well in disturbed soil; therefore areas with high construction and also roadsides will contain many of these plants.
Last Updated: 14 October 2009
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