Abstract: A rotary lawn mower grass mulcher assembly having a mower housing with a discharge opening over which two plates are disposed with each plate having airholes extending therethrough and with the holes being aligned offset between the two plates. Air is permitted to escape through the holes, but grass and like debris does not have free passage through the holes, and thus the mulcher assembly causes the grass clippings to remain in the mower housing for mulching or recutting action. The two plates are assembled together, and the plates are spaced apart with one thereof toward the outer end of the housing opening being angled downwardly and outwardly, all for permitting the passage of air but deflecting any debris downward to the ground.