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Allergy sufferers in Vienna should brace themselves: the tree‑of‑heaven (Ailanthus altissima) has officially entered its pollen season, which typically runs from early June to mid‑July. The reminder came Monday from the Pollen Service Vienna at MedUni/AKH Wien, which warned that this year’s bloom has begun earlier than usual due to persistent heat.
An invasive species on the rise
The tree‑of‑heaven, originally native to China and northern Vietnam, has spread aggressively across temperate and subtropical regions on every inhabited continent. Introduced to Europe as an ornamental plant in 1780—first planted in Berlin—it remained relatively contained until after World War II, when it began to proliferate rapidly.
Since 2019, it has been listed by the EU as an invasive species, and Austria actively works to curb its spread.
A unique allergen
Unlike classic wind‑pollinated allergens such as birch or grasses, the tree‑of‑heaven is primarily insect‑pollinated. Still, it releases large quantities of pollen during flowering, making it a growing concern for sensitive individuals.
Clinical data from China show sensitization rates of up to 30 percent among allergy sufferers, with smaller but notable rates observed in parts of Europe. However, standard allergy tests currently do not include tree‑of‑heaven pollen, and comprehensive European studies remain scarce.
A long‑term study by the Pollen Service Vienna now documents nearly 50 years of pollen data for the species in the capital—an important step toward understanding its impact.
Climate change fuels pollen production
According to MedUni Vienna’s long‑term measurements, temperature and hours of sunshine show the strongest correlation with pollen concentrations. The data reveal three clear trends:
- Rising pollen totals — overall pollen amounts have increased
- Earlier season start — flowering begins sooner
- Earlier season peak — the highest concentrations now occur earlier in summer
“With ongoing global warming, we must expect this trend to continue,” said Katharina Bastl of the Pollen Service Vienna. Urban areas like Vienna experience an additional boost from the urban heat island effect, which accelerates plant development and intensifies pollen release.
This year’s early bloom, the MedUni noted, is again linked to prolonged heat.
- source: vienna.at/picture: pixabay.com
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