The alders are found throughout most of North America and are very abundant in the Pacific Northwest. Depending on the location, the season can start from February to April. The season for alder is long in all areas because of the number of species found. Some of the species pollinate at different times. This is particularly true of the Pacific Northwest where the season can last as long as two to three months. Many people have allergic reactions to this pollen. All species are windborne and are reported to be significant allergens. There is high cross-allergenicity among this genus and cross reactivity with the pollen of Betula . They are considered highly allergenic
Carpinus sp., (hornbeans), Ostrya sp., (hop-hornbeans) and Corylus sp. (hazels) are related to the birch and alder and cross-reactions can occur. The hornbeans grow in the eastern parts of the U.S. and from Nova Scotia to eastern Manitoba in Canada. The hazels range from the East to Wyoming in the U.S. and from Newfoundland to British Columbia in Canada. We count the hornbeans and the hop-hornbeans in the birch look-a-like category. They pollinate mostly in May.
Last Updated: 31 August 2009
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