The rotary head (10) for garden trimmers, of the type with its cutter means (28, 30) pivoted to the head (10), comprises a lower shell (12) and an upper annular shell (14). The lower shell (12) is fixable coaxially to the trimmer drive shaft (20). The head presents several fixed pins (18) parallel to the rotational axis (10) of the head (10), for pivoting the cutter means (28, 30) provided with an eyelet. The upper shell (14) is coaxially applicable in its working position to the lower shell (12), in which position the cutter means (28, 30) are retained on the relative fixed pins (18), which project upwards from the lower shell (12). To apply the upper shell (14) to the lower shell (12) in said working position bayonet connection means (22, 24) are provided requiring a coaxial movement to cause the two shells (12, 14) to approach each other and a rotation of the upper shell (14) about the lower shell (12), this rotation being opposite to the direction of rotation (R) of the head (10) when working.
