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Ambrosia artemisiifolia


Scientific name: Ambrosia artemisiifolia L.

Common name: Ragweed (not to be confused with Ragwort, Senecio jacobaea).

Chromosome No.: 2n = 36 (Stace 2010).

Ambrosia artemisiifolia


It is widely distributed throughout the British Isles, with no particular pattern that relates to soil type, although there is a vague association with urban areas - especially around London for the older records. It appears to have been recorded in Ireland only since the BSBI Atlas in 2002. It is native to North America, but GBIF shows it to occur throughout Europe and in many other parts of the world.

BSBI Hectad Map 

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Origin: neophyte. It was first cultivated in Britain in the 18th century and was first recorded as a casual in the wild in 1836.

Rarity: if it were a native plant it would be classed as nationally scarce, because there are fewer than 100 dots for it in Britain, but as an alien it has no such status.

Threat: it is increasing in range and probably in abundance, possibly because there are more people putting out bird seed, but plants rarely persist.

Conservation: there is no suggestion that it is of value for nature conservation or poses any threat.


It is an annual weed that occurs as a casual and rarely persists. John Killick (in Preston, Pearman & Dines 2002) describes it as occurring on rubbish tips, in dockyards, arable fields, waste ground and wherever bird seed is put out. As a weed of arable crops it is difficult to control in fields of sunflower, as they are both members of the Asteraceae. In some parts of Europe it has become a rampant pest.

Further Work 

Arguably the most significant attribute of Ambrosia artemisiifolia is that its pollen is hyper-allergenic and, as it flowers late into summer it extends the hay fever season. Hay fever and asthma attacks can be uncomfortable or even life-threatening. The fear is that if it were to become established in the wild in Britain, as it is in Hungary and some other European countries, it could pose quite a hazard to the human population. Joe Crocker of the Food and Environment Research Agency is compiling information on A. artemisiifolia, and particularly wants to know:

a) If it is strictly casual - i.e. plants do not successfully reproduce in the wild.

b) If it chiefly (or only) arrives in birdseed, or if there are other modes of introduction.

If anyone can provide further information on populations they have encountered, please contact Joe 

  • Brandes, D. & Nitzche, J. 2006. Biology, introduction, dispersal and distribution of ragweed Ambrosia artemisiifolia with special reference to Germany. Nachrichtenbl. Deut. Pflanzenschutzd. 58, S 286-291.
  • Chauvel, B., Vieren, E., Fumanal, B. & Bretagnolle, F. 2004. Possibilite de dissemination d'Ambrosia artemisiifolia L. Via les semences de tournesol XIIème Colloque international sur la biologie des mauvaises herbes.
  • Dahl, A., Strandhede, S.-O. & Wihl, J.-Å. 1999. Ragweed – An allergy risk in Sweden? Aerobiologia 15: 293–297
  • Essl, F., Dullinger, S. & Kleinbauer, I. 2009. Changes in the spatio-temporal patterns and habitat preferences of Ambrosia artemisiifolia during its invasion of Austria. Preslia 81, 119-133.
  • Fumanal, B., Chauvel, B., Sabatier, A. & Bretagnolle, F. 2007. Variability and cryptic heteromorphism of Ambrosia artemisiifolia seeds: What consequences for its invasion in France? Annals of Botany 100, 305-313.
  • Genton, B.J., Shykoff, J. A. & Giraud, T. 2005. High genetic diversity in French invasive populations of common ragweed, Ambrosia artemisiifolia, as a result of multiple sources of introduction. Molecular Ecology 14, 4275-4285.
  • Hanson, C.G. & Mason, J.L. .1985. Bird seed aliens in Britain, Watsonia, 15, 237-252.
  • Kiss, L. & Beres, I. 2006. Anthropogenic factors behind the recent population expansion of common ragweed (Ambrosia artemisiifolia L.) in Eastern Europe: is there a correlation with political transitions? Journal of Biogeography 33, 2156-2157.
  • Laurer, V.M., Beitzinger, S. & Huber, K. 2009. Neophyten-Ausbreitung durch Vogelfutter. Anteil und Keimfähigkeit von Samen der Beifuß-Ambrosie (Ambrosia artemisiifolia) . Naturschutz und Landschaftsplanung 40, 244-247.
  • Lavoie, C., Jodoin, Y. & de Merlis, A.G. 2007. How did common ragweed (Ambrosia artemisiifolia L.) spread in Quebec? A historical analysis using herbarium records. Journal of Biogeography 34, 1751-1761.
  • Rich, T.C.G. 1994. Ragweeds (Ambrosia L.) in Britain. Grana 33, 38-43.
  • Vitalos, M. & Karrer, G. 2008. The contribution of bird seed, traffic and mowing machines to the spread of Ambrosia artemisiifolia. – In: Pyšek P. & Pergl J. (eds), Towards a synthesis: Neobiota book of abstracts, p. 120, Institute of Botany, Pruhonice.
Lockton, A.J. & Crocker, J. (date accessed). Species account: Ambrosia artemisiifolia. Botanical Society of the British Isles,