Ragweed (Ambrosia artemisiifolia) has become our most widespread weed. It causes a significant economic damage, on the other hand it causes pollen allergy affecting 20% of the country's population. Therefore its reduction has become a major task. An environmentally friendly method has been developed for its destruction by bioherbicides. This bioherbicid contains allochemical retardants. Allelochemicals are active chemical inhibition ingredients between plants (allelopathy). This method has been applied in the Kiskunság National Park (KNP) and the urban areas in the city of Kecskemét. We also present the typical therapeutic effect of ragweed, widely used in North American Indian culture.