Ambrosia artemisiifolia (common ragweed), an annual native to North America, is now
present in many European countries where it causes summer hay fever and interferes with
several important crops. We investigated if common ragweed invasiveness could be
explained by its leaf tissue and root exudate allelopathic potential on indicator crops (alfalfa,
barley, maize, lettuce, tomato, and wheat), weeds (Echinochloa crus-galli, Solanum nigrum,
Portulaca oleracea, and Digitaria sanguinalis), and common ragweed itself in laboratory and …