Tree pollen is dominant in the spring. May. Alder pollen season extends from January to April. The Betulaceae family consists of six genera which are found in the Northern Hemisphere, five of these are native to North America.
Most birches have very scaly bark.
Seven alder species are native to North America, all of which are pollinated by wind and shed copious amounts of pollen . Birch and Alder allergenicity Alder pollen can be found miles away from any source due to the abundance of pollen produced, their small size, and light weight. Many people have allergic reactions to this pollen. Common alder flowers from March to April. Smooth or Tag alder is among the first spring flowers, blooming in January and February in some regions.