Ragweed (Ambrosia spp.)

General Information

Family: Aster family (Asteraceae)
Flowering period in Central Europe:
Late summer to early autumn
Months: 8–9

Allergy potential
Very high allergenicity. Main allergen Amb a1. Irritations can occur even at low pollen concentrations (4 – 6 pollen grains per cubic meter of air). Frequently associated with asthma symptoms and rarely also contact allergies.

Cross-reactivity to other asters (e.g., arnica, mugwort, goldenrod, chamomile, sunflower) is possible.

Botanical Information

Originally North America. Introduced to Asia, Australia, and Europe after World War II. Invasive neophyte. In Austria, the densest occurrences are in Burgenland and Southern Styria (see Habitats - Disturbed soils (roadside verges, fields, construction sites).

Habit - Annual or perennial herbaceous. Foliage — Leaves stalked or unstalked, leaf blade simple to pinnate, leaf margin smooth to serrated, leaf underside green (distinguishing feature from mugwort). Reproduction — Partial flower heads in basket-like in branched inflorescences, hairy stems.