A lawn mower includes a housing with a baffle that defines an air path to produce a cross-flow. The baffle includes a vent to manipulate air pressures within the housing and facilitate movement of plant clippings. A hand-held device for trimming with a rotary blade assembly may also include a housing that defines an air path to produce a cross-flow. The hand-held trimming device may also a baffle with a vent to facilitate movement of plant clippings.