Abstract: A blade assembly for a lawn mower has a generally planar body (1) rotationally balanced about a vertical central shaft (24), with four projecting blades (6) extending radially from the periphery of the planar body. The planar body (1) is shaped with vanes (3) to form a fan-like impeller. The impeller is arranged to create a strong rotational flow, which carries air and cut material around the blade assembly in use. The projecting blades (6) create an updraft in a peripheral region of the blade assembly, while the vanes (3) of the planar body (1) are shaped to create a regulated, relatively light downdraft towards the central shaft (24). If the mower is provided with an outlet (25) for a catcher, the strong rotational flow overwhelms any influence of the relatively light downdraft, and the air with the clippings is carried centrifugally through the outlet (25).