A shearing mechanism for a tree harvester having a pair of arms each carrying a weighted shear blade at one end and affixed at the other end to each of a pair of parallel shafts supported by the harvester with the shafts being rotated in opposite directions to move the arms between a first position in which the shear blades face outwardly in opposite directions from upwardly extending arms and a second position in which the shear blades face inwardly adjacent each other in opposite directions from downwardly extending arms.