
Allergy sufferers in Vienna and eastern Austria need to be prepared for the start of the hazel pollen season. The first plants in sunny locations are ready to flower. Pollen concentrations are currently only occurring locally. In general, a below average hazel pollen season is expected for Vienna. However, those affected should now think about taking precautions and regularly inform themselves about the situation. As usual the Spaeth’s alder has already started to flower at the end of December and already finished flowering in Vienna. This city tree causes hardly any measurable pollen concentrations, but can cause localized discomfort. This is reported by the Vienna Pollen Service of MedUni Vienna.
To be precise, the 2025 pollen season already began in 2024 in the last days of December with the flowering of the Spaeth’s alder. This tree species is a hybrid and withstands the urban climate well. Unfortunately, its early flowering extends the alder pollen season.
The catkins of the gray alder (Alnus incana) and the black alder (Alnus gutinosa) are still firmly closed. In Vienna, the gray alder starts to flower before the black alder in the end of January at the latest, depending on the weather conditions.
Hazel pollen season begins
The hazel pollen season has not yet begun. However, the first plants are ready to flower in sunny locations. Reports from our neighbouring country, Germany, also informed about the start of hazel pollen season in the last days. With sunshine and temperatures above 5°C, the first pollen concentrations can be expected in Vienna too.Keeping your eyes open is extremely important, as Maximilian Bastl from the Vienna Pollen Service at MedUni Vienna recommends: "Recognizing flowering plants and avoiding the vicinity is a great advantage. Pollen concentrations are many times higher in the immediate vicinity of the source."
There is also good news: The flower of hazel will be 2025 below average after an already below average season in 2024. The number of catkins, that produce pollen, is the second year in a row low. Especially, the tree hazel shows hardly any catkins (apart from a few exceptions).
365 days a year Pollen Service Vienna
Pollen concentrations are measured and recorded by the Pollen Service Vienna 365 days a year. The pollen forecasts and the information on the website are also updated at least weekly at all times of the year (as was the case last winter). This ensures the desired high quality of the pollen forecasts. The observation of nature and in particular the development of the flowering stages of allergenic plants at different locations is an important part of the work.
The importance of science
High quality can only be achieved by being rooted in science. Climate change is already causing significant changes in the pollen season. MedUni Vienna has carried out pioneering work in this area: for the first time, a study has shown a significant change in the mugwort pollen season in Austria. Such changes can only be addressed and adequately responded to by working flexibly, as practiced at MedUni Vienna, and by interlinking with research. Pollen dispersal models reach their limits due to extreme weather phenomena and strongly fluctuating temperatures. The future of pollen forecasting therefore means, above all, precise and regular monitoring of nature. Of course, this must also be performed locally. A metropolis like Vienna requires special attention, and not just because of the "urban heat island effect". The somewhat warmer conditions in the city generally mean that plants can start flowering a little earlier than in other areas of Austria.