The natural product dehydrozaluzanin C (former DHZ) is a sesquiterpene lactone obtained from different weeds of the Compositae family. Its potential as a plant growth regulator has been evaluated by using a phytotoxic allelopathic bioassay, where the commercial herbicide Logran is used as internal reference. The evaluation is made based on their effects on germination and growth over several dicotyledon and monocotyledon species. The activity was tested in the range of 1000-0.001 microM. In almost all cases, DHZ was more active than the internal reference at 1000 microM, and its activity fell below the level of the internal reference at 100 microM. These results confirm DHZ as a potent plant growth regulator and a good candidate for the development of new herbicide models.