The aim of this work is to study in a pulsed magnetron discharge of acetylene at 10−1 Torr, the influence of tOFF parameter on roughness and morphology of films deposited on silicon substrates. By using a low power discharge (long tOFF and short tON for a given power), a coating with unique morphology is deposited. This film is formed of nanoparticles and particular agglomerates called ‘flowers’ of micrometric size. To the best of our knowledge, it's the first time that such ‘flowers’ structures have been observed for a pulsed plasma polymerization of acetylene. According to the obtained results in mass spectrometry of plasma, nanoparticles and ‘flowers’ are probably formed in gas phase. A growth mechanism in several steps is proposed.