Ambrosia, ragweed and giant hogweed are all dangerous for humans and animals. Ambrosia contains the strongest pollen allergen in the world.
Giant hogweed causes painful burns on the skin and overrides the skin's natural UV protection. ragwort is an ancient native plant and can spread very well thanks to its long-lived seeds. occupational herb daisy is a neophyte and displaces native (endangered) plants in some areas of Germany. It is also dangerous for horses, but also for cattle.