Ambrosia - irritating danger

Luise Heine has been an editor at since 2012. The qualified biologist studied in Regensburg and Brisbane (Australia) and gained experience as a journalist in television, in the Ratgeber-Verlag and in a print magazine. In addition to her work at , she also writes for children, for example for the Stuttgarter Kinderzeitung, and has her own breakfast blog, “Kuchen zum Frühstück”.

More posts by Luise Heine All content is checked by medical journalists.

So far you can find them mainly in southern and eastern Germany. But wherever it occurs, it spreads terror in allergy sufferers: the mugwort ragweed. Their pollen triggers severe hay fever complaints - even in the smallest quantities. Is it still possible to master the ominous herb?

The problem is actually not that new: the sagebrush ragweed (Ambrosia artemisiifolia) was introduced from North America to Eastern Europe around 150 years ago. From there the plant found its way to Germany via contaminated bird seed. "But it wasn't until the hot, long summers in 2003 and 2006 that the Ambrosia started to spread across the board, too," explains meteorologist Thomas Dümmel from the Free University of Berlin.

The ambrosia is a climate change winner. Because if there is one herb that cannot stand, it is ground freeze sooner. This destroys the plant with its seeds in no time at all. In the two summers of the century, however, ample ragweed was able to complete its life cycle and spread its seeds into the ground - experts call this the “seed bank”. The capsules rest in the ground as small time bombs. You can wait up to 40 years for conditions to be inviting to germinate.

Potent allergy trigger

Ambrosia is feared above all because of its pollen: each individual plant can send up to a billion pollen grains into the wind per season. And they have it all: three quarters of all pollen allergy sufferers react to the pollen. "Five to ten pollen grains per cubic meter of air can be enough for this," says Dümmel. In comparison: To achieve a similar effect, the birch needs 20 to 30 pollen grains. Ambrosia pollen is also very small and can therefore penetrate deeper corners of the lungs - inflamed bronchi and even asthma are not uncommon consequences. That is why the inconspicuous plant is considered one of the most dangerous natural allergy triggers.

Experts are not only concerned about the allergy potential of pollen. “The ragweed also blooms relatively late in the year - from July to October,” the plant expert knows. So far it was a period in which many hay fever sufferers had peace again. The sagebrush ragweed extends the season for sniff noses and watery eyes. Not only people who already have hay fever are at risk. "Everyone can become allergic, so there doesn't have to be a previous exposure to other pollen," says Dümmel.

A horror scenario: In America, ragweed is responsible for a large part of pollen allergies.The fact that it is on the advance here, too, has consequences for the wallet - in Germany, according to estimates by experts, ragweed already costs between 17 and 47 million euros annually in the healthcare system.

To tackle the problem at the root

The good news: The evil can literally be tackled at the root. For a number of years, for example, “Ambrosia Scouts” have been swarming in Berlin under the guidance of experts like Thomas Dümmel. They map the occurrence of the plant and thus create the basis for its elimination. These measures, together with the favorable weather, have ensured that the problem in the German capital is largely kept in check at the moment. "But the federal states all deal with the situation very differently," says Dümmel. Some rely on government agencies, others ignore the problem and leave the fight to volunteers who organize themselves.

In fact, anyone can help contain the threat by keeping an eye out for ragweed. This, however, takes a little practice, because the herb is rather inconspicuous. Accordingly, it is difficult for the layperson to distinguish the unwanted greenery from other plants. The highly branched plant can vary in height, for example between 15 and 180 centimeters - that is an enormous range. However, there are some features that the trained eye can use to identify ragweed. The underside of the pinnate leaves is not very hairy and green - an important distinguishing feature from the similar-looking mugwort, which has a silvery underside of leaves. When in doubt, there is botanical literature to help determine.

Pioneer plant

The ragweed is dependent on a lot of light, which is why it is mainly found in open areas with strong sunlight. "From the end of May it will be worthwhile to look out for the plants," explains Dümmel. If the subsoil is heavily overgrown, the ambrosia will usually not germinate. Classic habitats are construction sites, fields and fallow land - the ragweed is a pioneer plant. However, it is dependent on human help for the spread. For example, the seeds travel along roads and paths in tire treads and on shoes, or are distributed when the birds are fed.

The problem with birdseed should hopefully soon be resolved, because an EU regulation from 2011 forces suppliers to keep their seed mix as free as possible from contamination. Nevertheless, it is still worth taking a close look at your own bird food. "The ambrosia seeds look like morning stars - small balls with spikes on them," Dümmel provides assistance. Usually they can be easily distinguished from the more flat seeds like sunflowers. So far, however, it is still worth looking for ragweed in places where bird seed has been applied, for example around the open areas around trees or under balconies.

Plastic bag over and away with it

What if you find ambrosia in your own garden? "If the plant is not yet in bloom, you can simply tear it up," says Dümmel. But if you are not sure what phase the plant is in, you should put a plastic bag over it before plucking it out. In this way, on the one hand, you prevent skin contact, which can be irritating to sensitive people, and, on the other hand, you don't involuntarily spread the pollen or seeds, the expert advises. Then simply put the sack in the household rubbish. And: You should report the occurrence to the authorities - if your own federal state has a corresponding office - or to the “Ambrosia Atlas” website.

Targeted search and extermination campaigns help to make life difficult for Ambrosia in Germany. But can this also prevent their further spread? “In principle yes,” says the meteorologist: “The fight has not yet been won, but at least we know how to wage it.” For this, it is important to create a broad awareness of the danger and bundle it with appropriate, financial ones To take action against it. This would prevent scenarios like those in America. "Switzerland is a shining example," says the expert, "they have meanwhile got the ambrosia under control."

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