A lawnmower is convertible between a bagging mode and a mulching mode. The convertible lawnmower includes a cutter housing having a discharge opening, an engine mount centrally positioned on the cutter housing, a prime mover supported on the engine mount, a rotary mulching blade coupled to the prime mover to rotate in a cutting plane about a rotation axis within the cutter housing, a cover and a fin extending from the cover toward the cutting plane. The cover is movably mounted within the cutter housing in a plane parallel to the cutting plane and between a full bagging position where the discharge opening is unobstructed by the cover and a full mulching position where the cover obstructs the discharge opening.