A trimmer head for a trimmer, the trimmer head comprising: a base plate defining an axial direction; a pivot head attached to the base plate, the pivot head comprising: an extended post having a blade support surface to selectively receive a flail blade, and a main body positioned between the extended post and the base plate relative to the axial direction, the main body defining a string slot to receive a trimmer string line therethrough; characterized by a blade retainer comprising a radial arm rotatably mounted to the base plate to rotate relative to the base plate between a first position at which the radial arm is circumferentially aligned with the pivot head and a second position at which the radial arm is circumferentially spaced apart from the pivot head, wherein the blade support surface is positioned between the base plate and the radial arm relative to the axial direction, wherein the blade retainer further comprises: a mounting arm rotatably mounted to the base plate below the blade support surface relative to the axial direction; and an axial arm extending axially from a proximal end at the mounting arm to a distal end at the radial arm. a base plate defining an axial direction; a pivot head attached to the base plate, the pivot head comprising: an extended post having a blade support surface to selectively receive a flail blade, and a main body positioned between the extended post and the base plate relative to the axial direction, the main body defining a string slot to receive a trimmer string line therethrough; characterized by a blade retainer comprising a radial arm rotatably mounted to the base plate to rotate relative to the base plate between a first position at which the radial arm is circumferentially aligned with the pivot head and a second position at which the radial arm is circumferentially spaced apart from the pivot head, wherein the blade support surface is positioned between the base plate and the radial arm relative to the axial direction, wherein the blade retainer further comprises: a mounting arm rotatably mounted to the base plate below the blade support surface relative to the axial direction; and an axial arm extending axially from a proximal end at the mounting arm to a distal end at the radial arm. an extended post having a blade support surface to selectively receive a flail blade, and a main body positioned between the extended post and the base plate relative to the axial direction, the main body defining a string slot to receive a trimmer string line therethrough; characterized by a blade retainer comprising a radial arm rotatably mounted to the base plate to rotate relative to the base plate between a first position at which the radial arm is circumferentially aligned with the pivot head and a second position at which the radial arm is circumferentially spaced apart from the pivot head, wherein the blade support surface is positioned between the base plate and the radial arm relative to the axial direction, wherein the blade retainer further comprises: a mounting arm rotatably mounted to the base plate below the blade support surface relative to the axial direction; and an axial arm extending axially from a proximal end at the mounting arm to a distal end at the radial arm. a blade retainer comprising a radial arm rotatably mounted to the base plate to rotate relative to the base plate between a first position at which the radial arm is circumferentially aligned with the pivot head and a second position at which the radial arm is circumferentially spaced apart from the pivot head, wherein the blade support surface is positioned between the base plate and the radial arm relative to the axial direction, wherein the blade retainer further comprises: a mounting arm rotatably mounted to the base plate below the blade support surface relative to the axial direction; and an axial arm extending axially from a proximal end at the mounting arm to a distal end at the radial arm. a mounting arm rotatably mounted to the base plate below the blade support surface relative to the axial direction; and an axial arm extending axially from a proximal end at the mounting arm to a distal end at the radial arm.