Video Highlight: flower of black alder 2025
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The black alder is flowering in Vienna. The majority of the catkins are in bloom and ready to dust, as can be clearly seen here in the macro video (©Katharina Bastl (MedUni Vienna/Pollenservice Vienna)).
The main pollination period of the black alder in Vienna usually extends from February to March. This year, the main flowering period began in calendar week 8.
Video Highlight: flower of hazel 2025
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The hazel flowers in Vienna. The pollen grains are too small for the naked eye and are only in the shape of a pollen cloud to see, as can be clearly observed here in the video (©Katharina Bastl (MedUni Vienna/Pollenservice Vienna)).
Pollen is only released when the catkins are in bloom. Each male catkin can contain millions of pollen grains (between 2 and up to 8 million depending on the reference).