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.
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.
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
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