Mulchers with vertical axis of rotation are highly energy demanding machines and it is expedient to increase their effectiveness. The paper deals with evaluation of the effect of the shape of mulcher’s workspace cover on energy demands and pressure conditions of the workspace of mulcher with vertical axis of rotation. The pressure conditions inside the workspace are connected with the airflow which is vital for the correct function of the machine. The laboratory model of one mulcher’s rotor was used for the measurement. Three workspace cover shapes were used for the measurement, including shapes called “drop”, “toroid” and flat cover which was used as a reference. The measurement was carried out at cutting speeds of 21, 42, 63, 84 and 105 ms-1. The proposed shapes of mulcher’s workspace cover showed higher energy demands, while the cover in shape “toroid” significantly affected the pressure profile in the mulcher workspace.