It is widely known that Orobanche cumana seeds need a conditioning phase of several days under suitable temperatures and wet conditions before being able to germinate in response to germination stimulants. In a series of experiments we showed that O. cumana seeds respond to the synthetic germination stimulants Nijmegen-1 and GR24 even without prior conditioning. These results are consistent with our hypothesis that, under certain field circumstances, non-conditioned Orobanche seeds may also germinate when a host root comes close to them.