Abstract: A vortex reducing mower blade for use with a rotary lawn mower having a motor and a depending drive shaft has a cutting edge on each leading edge thereof, an airlift on each trailing edge thereof, and outboard ends extending between the terminations of the leading and trailing edges. The outboard ends generally meet with the trailing edges at respective trailing corner- or tip-regions. Each outboard end has margins formed as a boundary-layer fence that is angled either upwardly or downwardly relative to a given relative up direction which is parallel to the central axis of the depending drive shaft. These boundary-layer fences reduce the production and/or strength of vortices in the wake of the trailing corner- or tip-regions of the blade. Each boundary-layer fence may be angled either upwardly or downwardly at generally a right angle.