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Many allergy sufferers react to the highly pathogenic birch pollen with watery eyes, sneezing and breathing difficulties. The tree with the distinctive white trunk produces a particularly large amount of pollen. You can find out when these fly in this article.

In a nutshell

  • Main flowering time is in April
  • Bee pollen can also fly from February and until the end of August
  • Pollen count depends on the weather
  • from temperatures of 15 degrees Celsius and in sunny weather

birch blossom

Birch trees (Betula) have a fairly long flowering period, the beginning and end of which depend on the weather:

  • Main bloom in April
  • Duration around two weeks
  • begins at temperatures above 15 degrees Celsius
  • and after a few days of dry sunny weather
  • if the weather is good, pollen count as early as the end of February

Since birches are so-called monoecious plants, male and female flowers are on the same tree. The male flowers, called catkins, appear in the previous year and overwinter on the older shoots. They are up to ten centimeters long and hang down from the branch.
Only the male flowers emit the yellow pollen, because birch trees, as pioneer plants, depend on wind pollination. This is why these trees produce a particularly large amount of pollen compared to other species - up to five million pollen grains per flower. The highly allergenic pollen is recognizable as a fine, yellow cloud and often covers window panes and car roofs during the main flowering period.

Notice: About every two years there is an event that botanists call the "mast year". During these years, birch trees emit even more pollen than usual, which is a particular burden for allergy sufferers.

Pollen load after mild winters

However, after a mild winter, birch trees can bloom much earlier, so exposure to birch pollen lasts for a much longer period. Therefore one speaks of a main and a secondary flowering, during which different amounts of pollen are released. Since the pollen-giving male flowers overwinter on the tree, the first pollen flight can even occur in winter if the weather is suitable. So you should remain vigilant in temperatures above 15 degrees Celsius and sunny weather.
Pollen count calendar for the birch:

  • Main flowering: particularly heavy exposure to birch pollen in April
  • Before and after flowering: moderate pollen count between mid-March and late May
  • possible occurrence: lower pollen load possible from February to the end of August

Allergic symptoms, such as shortness of breath, are particularly severe when it is very hot or after heavy rain or a thunderstorm.

frequently asked Questions

When does birch pollen fly the strongest?

The time of day when birch pollen fly depends primarily on where you live. In the city, the exposure is highest between 6:00 p.m. and 8:00 p.m. In rural areas, on the other hand, it is between 5:00 a.m. and 8:00 a.m. in the early morning. So if you're a city dweller, ventilate the room in the morning if possible, and if you're a country dweller, ventilate it in the evening until around midnight.

Why does an allergy worsen when it rains?

Allergy sufferers are actually happy about rain while birch trees are in bloom - they can breathe easy during this time. However, it is different in heavy rain or even thunderstorms: Here the birch pollen bursts as a result of the osmotic shock and releases huge amounts of allergens. Therefore, always keep the windows closed during heavy rain or a summer thunderstorm.

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