An apparatus for use with a vehicle to reduce plant material includes a frame having first and second mounting brackets, a boom coupled to the frame and having first and second mounting plates, a drive assembly having a drive shaft, a cutting device rotatable with the drive shaft, a reinforcing member to support the boom, a first bearing assembly sandwiched between the first mounting bracket and the first mounting plate, and a second bearing assembly sandwiched between the second mounting bracket and the second mounting plate. Each bearing assembly has an exterior annular member, an interior annular member, and a rolling element disposed between the interior and exterior members. The rolling element permits movement of the exterior and interior members relative to one another to facilitate rotation of the mounting plate relative the mounting bracket to permit pivotal movement of the boom relative to the frame.