Unusually early flowering of alder in Vienna: first report of Alnus x spaethii in Austria, combined LM and SEM study of alder species and impact on pollen allergy sufferers

Different species of alder cause hay fever symptoms in pollen allergy sufferers within Europe: Alnus glutinosa (black alder), A. incana (grey alder), A. viridis (green alder) and more recently A. x spaethii (japonica x subcordata; Spaeth's alder). In Austria, the alder pollen season usually lasts from January to April (until June in the mountains due to later flowering of A. viridis). The pollen season started very early in 2014, namely by the end of December 2013 in Vienna with the first pollination of alder. Such an early flowering around Christmas is known for A. x spaethii and was first recognized as problem in Switzerland. Up to now, this alder species was not reported in Austria. A sample including twigs, leaves, catkins and pollen from Switzerland was compared with an unusually early flowering alder in Vienna. The pollen of these (Alnus x spaethii) and in addition from black and green alder was analysed by light microscopy and scanning electron microscopy to find possible morphological differences or similarities in their pollen morphology. The general morphology revealed that A. x spaethii is present in Austria (planted in a park) and was responsible for the first burden on pollen allergy sufferers during the alder pollen season in Vienna, although pollen data revealed no significant alder pollen concentrations. The results emphasize the importance of monitoring phenology for pollen information.