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Spring is coming and the birch will sprout again and form a large number of pretty flowers, the catkins. But the birch pollen from the flowers, which is dispersed by the wind, is one of the most common triggers for allergies such as hay fever and the like.
In a nutshell
- Flowering time from mid-March to late May
- Main load in mid-April
- every 2 years mast year with particularly high pollen density
- are among the strongest tree pollen allergens
Flowering time & pollen count
Birch trees (Betula) usually have their main flowering period in two weeks in mid-April. Depending on the weather, however, this period may change. If the winter was very mild and the temperatures rose above 15 degrees Celsius early on, the pollen count can begin as early as the end of February and last into August. The pre- and post-flowering is usually between mid-March and the end of May.
In Germany, these four types of birch are most common:
- Dwarf birch (Betula nana)
- Tree birch (Betula humilis)
- downy birch (Betula pubescens)
- Silver, Silver, Silver or Wart Birch (Betula pendula)
Notice: Birch trees bloom for the first time after only 5 years of growth.
birch pollen
Only male flowers contain the allergenic birch pollen.
- Kittens up to 10 cm long
- Buds about 4 mm in size
- form in the previous year and overwinter
- are not pollinated by insects but by the wind
- therefore up to 5 million pollen per kitten possible
Birch trees have a so-called mast year every 2 years. The trees produce a particularly large amount of blossoms and pollen, which again significantly increases the burden on allergy sufferers.
Allergic reactions are particularly common in the following weather conditions:
- Strong heat
- rain
- thunderstorm
frequently asked Questions
What are the mast years dependent on?The formation of the flowers in the mast year is also dependent on the weather. If the blossoms are destroyed by late frost in spring, the birch produces an extremely large number of new blossoms in the same year for a successful distribution of birch pollen. After hibernation, in the mast year, the pollen count is all the greater.
Is the pollen count the same for all birch species?All birch species are pollinated by wind. Therefore, the male kittens form a comparably high number of pollen. The flowering time is also the same for the different species.
Does birch pollen cause cross allergies?Yes, allergies to birch pollen often go hand in hand with other allergies, e.g. to fruit or nuts. The immunoglobulin E antibodies of the immune system then also target other, similar allergens.