 He is associated with the Düsseldorf school of painting.A notable student of his was the Norwegian landscape painter Adelsteen Normann who studied with Dücker from 1869 to 1872.Other pupils included Heinrich Hermanns, Franz Korwan, Georg Macco, Otto Modersohn, Fritz Overbeck, Edgar Meyer, Heinrich Petersen-Angeln, Oskar Hoffmann and Carl Wuttke.