SLU news

Risk for establishment of common Ragweed in Sweden - great allergi problem

Published: 23 November 2016

The invasive weed Ambrosia artemisiifolia (common ragweed) constitutes a great threat to public health and agriculture in large areas of the globe. Climate change, characterized by higher temperatures and prolonged vegetation periods, could increase the risk of establishment in northern Europe in the future, according to researchers from SLU and their colleagues in Croatia and Germany.

However, as the species is a short-day plant that requires long nights to induce bloom formation, it might still fail to produce mature seeds before the onset of winter in areas at northern latitudes characterized by short summer nights.

To survey the genetic variation in flowering time and study the effect of latitudinal origin on this trait the researchers conducted a reciprocal common garden experiment, including eleven populations of A. artemisiifolia from Europe and North America.

The experiment was conducted both outside the range limit of the species, in Sweden and within its invaded range, in Croatia. Their main hypothesis was that the photoperiodic-thermal requirements of A. artemisiifolia constitute a barrier for reproduction at northern latitudes and, thus, halts the northern range shift despite expected climate change.

Results revealed the presence of a north-south gradient in flowering time at both garden sites, indicating that certain European populations are pre-adapted to photoperiodic and thermal conditions at latitudes up to, at least, 60° N. This was confirmed by phenological recordings performed in a region close to the northern range limit, the north of Germany.

Thus, the researchers conclude that there exists a high risk for establishment and spread of A. artemisiifolia in FennoScandinavia in the near future. The range shift might occur independently of climate change, but would be accelerated by it.


Lars Andersson, Professor and External Collaboration Specialist in plant production
Department of Crop Production Ecology, SLU, +46 (0)18-67 33 66, +46 (0)70-344 39 76