an assembly for mounting on a power lawnmower for collecting grass clippings and the like in a disposable flexible container . the assembly includes a support for maintaining the flexible container in a substantially upright position with an open top and located rearwardly of the lawnmower housing . a cover is pivotally carried on the support and encloses the open top of the flexible container . the cover and the flexible container cooperate to define a substantially enclosed chamber . spaced inlet and outlet openings are provided in the chamber . an inlet channel , extending upwardly and rearwardly from the mower housing , is connected to the inlet opening for discharging yard clippings into the flexible container . an exhaust assembly communicates with the outlet and the exterior . the opening faces in a direction away from the operator of the lawnmower . a separator is mounted in the cover to separate the clippings and other solids from the air so that the exhaust air is substantially free of such solids as it passes through the exhaust .