table of contents
- Birch blossom
- Pollution after mild winters
- frequently asked Questions
Many allergy sufferers react to the highly pathogenic pollen of the birch 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 they fly in this article.
In a nutshell
- The main flowering time is in April
- Bee pollen can also fly from February until the end of August
- Pollution levels depend on the weather
- from temperatures of 15 degrees Celsius and in sunny weather
Birch blossom
Birch trees (Betula) have a long flowering period, the beginning and end of which depend on the weather:
- Main bloom in April
- Duration around two weeks
- starts at temperatures above 15 degrees Celsius
- and after a few days of dry, sunny weather
- if the weather permits, pollen counts from the end of February
Since birch trees are so-called monoecious plants, there are male and female flowers on the same tree. The male flowers, called catkins, appear in the previous year and overwinter on the older shoots. They are up to four inches long and hang down from the branch.
Only the male flowers emit the yellow pollen, because birch trees, as pioneering plants, are dependent on wind pollination. That's why they produce them Trees a particularly large amount of pollen compared to other species - up to five million pollen grains per flower. The highly allergenic pollen can be seen as a fine, yellow cloud and often covers window panes and car roofs during the main flowering period.
Note: About every two years there is an event which botanists refer to as the “fattening year”. In these years birch trees emit even more pollen than usual, which is particularly stressful for allergy sufferers.
Pollution after mild winters
However, after a mild winter, birch trees can bloom much earlier, so that the birch pollen load extends over a much longer period of time. That is why one speaks of a main flower and a secondary flower, during which different amounts of pollen are released. Since the pollen-donating male flowers hibernate on the tree, the first pollen flight can even occur in winter if the weather is right. So you should be careful in temperatures above 15 degrees Celsius and sunny weather.
Pollen calendar for the birch:
- Main flowering: particularly heavy load from birch pollen in April
- Pre- and post-flowering: moderate pollen count between mid-March and the end of May
- possible occurrence: lower pollen load possible from February and until the end of August
Allergic symptoms such as shortness of breath in extreme heat or after heavy rain or a thunderstorm.
frequently asked Questions
The time of day birch pollen flies depends primarily on where you live. In the city, the exposure is highest between 6:00 p.m. and 8:00 p.m., in the countryside, on the other hand, in the early hours of the morning between 5:00 a.m. and 8:00 a.m. As a city dweller, therefore, ventilate in the morning if possible, and as a rural dweller in the evening until around midnight.
People with allergies are actually happy about the rain while birch trees are in bloom - this is when they can breathe a sigh of relief. However, it looks different in heavy rain or even thunderstorms: Here the birch pollen bursts as a result of the osmotic shock, releasing vast amounts of allergens. Therefore, always keep the windows closed in heavy rain or a summer thunderstorm.