Ragweed (Ambrosia)

Family:

Daisy family (Asteraceae)

Flowering period:

August-September

Distribution:

mainly native to North America, introduced from there to Europe, Asia and Australia, invasive, is spread by humans through contaminated bird food and construction equipment, spreads particularly in ruderal habitats and disturbed soils (roadsides, gravel pits, rubbish dumps and construction sites)

Appearance:

annual to perennial herbaceous plants, leaves are alternate or opposite, petiolate or sessile, the leaf blade is simple to pinnate to the leaf edges are smooth to serrated, in contrast to mugwort the lower leaf surface is green, the cup shaped male flowers are borne in terminal candle-like inflorescences, females appear in leaf axes underneath, hairy stems

Important species in Europe:

Ambrosia artemisiifolia (common ragweed): can grow up to 1.8 m high in Central Europe, annual

Ambrosia trifida (giant ragweed): three pinnate leaves (grows up to 4m high)

Ambrosia psilostachya (Perennial ragweed): predominantly spread through their roots, thus produces fewer seeds than A. artemisiifolia

Allergenicity:

responsible for "fall hay fever", highly allergenic, a few pollen grains per m3 of air are sufficient to cause irritation, often leads to asthma as well as skin symptoms (dermatitis), cross-reactions with goldenrod, sunflower, chamomile, Arnica and other Asteraceae are possible, Amb a1 is the main allergen

Link zum Pollenatlas: Ambrosia artemisiifolia