Ambrosia artemisiifolia (image) University of Washington Share Print E-Mail Caption Common ragweed, Ambrosia artemisiifolia, is common in North America and is spreading in Europe. The plant releases a fine pollen in late summer and fall that causes allergy symptoms in people with hay fever. Credit Andreas Rockstein/Flickr Usage Restrictions With credit Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.