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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

Wissenschaftlicher Beirat:
Ass. Prof. Dr. Siegfried Jäger (Medizinische Universität Wien)
Univ. Prof. Dr. Reinhart Jarisch (Floridsdorfer Allergie Zentrum)
Mag. Matthias Werchan (Charité Berlin)
Prof. Dr. med. Karl-Christian Bergmann (Charité Berlin)

Quellen:

Österreichischer Pollenwarndienst, Medizinische Universität Wien, Österreich
Charité, Allergie-Zentrum-Charité, Klinik für Dermatologie, Venerologie und Allergologie, Berlin, Deutschland
Wikipedia
www.alles-zur-allergologie.de
22 Jahre Blüh- und Fruktifikationsuntersuchungen der Waldbaumarten im Lehrforst Ofenbach/Rosalia. R. Litschauer. 2010. Bundesforschungs- und Ausbildungszentrum für Wald, Naturgefahren und Landschaft, BFW-Berichte 144, 36 pp.
Waldbau auf soziologisch-ökologischer Grundlage. H. Mayer 1977. Gustav Fischer Verlag, Stuttgart – New York, 482 pp.

Flowers, “daisy flower”, of ragweed in detail (Image rights: Katharina Bastl)
Flowers, “daisy flower”, of ragweed in detail (Image rights: Katharina Bastl)
Flowers if ragweed (Image rights: Katharina Bastl)
Flowers if ragweed (Image rights: Katharina Bastl)
Habit and leaves of ragweed (Image rights: Katharina Bastl)
Habit and leaves of ragweed (Image rights: Katharina Bastl)
Young and immature ragweed plant (Image rights: Katharina Bastl)
Young and immature ragweed plant (Image rights: Katharina Bastl)
Location with several ragweed plants (Image rights: Katharina Bastl)
Location with several ragweed plants (Image rights: Katharina Bastl)
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