First impressions of the 2025 pollen season and preview for the coming months

The pollen season actually starts around Christmas time in some regions of Austria. This is when the purple alders (Alnus x spaethii), which are often planted as park and avenue trees, are ready to bloom. These trees are hybrids, i.e. crosses between two alder species, the Japanese alder (Alnus japonica) and the Caucasian alder (Alnus subcordata), which, unlike many other members of the Alnus genus, begins to flower at the end of December.1-4 However, as the purple alder is less common than the native species such as gray alder (Alnus incana), black alder (Alnus glutinosa) or green alder (Alnus viridis), pollen concentrations in the air that can lead to allergic reactions are generally only to be expected in the immediate vicinity of larger populations.