A bump-activated trimmer head for a rotary trimmer of the type that utilizes wound trimmer line to cut vegetation, the trimmer having a rotary shaft defining a rotation axis, a housing attached to the rotary shaft, at least a pair of opposed eyelets through the housing for receiving the trimmer line, a spool encased within the housing and having a passageway for the trimmer line, the opposed ends of the passageway being alignable with the opposed eyelets of the housing. The trimmer head further includes an indexing knob external to the housing and operatively connected to the spool for turning the spool so as to wind the trimmer line onto the spool, and a separate bump knob rotating about the same rotation axis as the shaft, wherein the bump knob is operationally connected to the spool, but is rotationally independent of the shaft, the housing and the spool.