Common Ragweed (Ambrosia artemisiifolia), is the most widespread plant of the genus Ambrosia in North America. It has also been called Annual Ragweed, Bitterweed, Blackweed, Carrot Weed, Hay Fever Weed, Roman Wormwood, Stammerwort, Stickweed, Tassel Weed, and American Wormwood. It is native in North America, but it is spreading in large areas in Europe, too. It is not only an agricultural problem, but also human health problem, causing alergic reactions. In Hungary they identified also airborne pollen of Ambrosia elatior. The pollen of both Ambrosia species occures in the air in July and August.