In a mower of the cross-flow blower type the rotor of the blower has a plurality of sections with predetermined blades of at least two adjacent sections of opposite helix angle and having cutting edges which overlap in the axial direction and are angularly spaced about the rotor axis in the overlap region, thereby producing counteracting axial components of air velocity. Preferably at least one blade in each section is shorter than the rotor length and advantgeously all blades in a section are shorter, with ends angularly spaced from and overlapping the ends of the blades of adjacent sections. Preferably each section has blades of opposite helix angle to produce counteracting components of air velocity in each section. Advantgeously each section of the rotor is formed of an integral sheet bent to form end supports and a pair of blades of opposite helix angle. The blades are preferably of the hook type with the leading edges of the hooks serrated. Marked reduction in blower noise can be attained, with good mower performance.