A cutter vehicle is arranged to be moved along a row of trees by a powdered drive vehicle. A boom assembly is secured between the cutter vehicle and the drive vehicle and has relatively movable parts which can extend and retract to vary the longitudinal length of the boom assembly. The cutter vehicle has a powered cutter arranged to cut a tree off adjacent the ground. The mechanism has controls capable of actuating the power cutter substantially simultaneously with release of the power for the boom assembly whereby the movable parts of the boom assembly can have free relative movement to allow the powered drive vehicle to advance while the cutter vehicle has stopped momentarily to cut a tree, this providing an arrangement which allows a drive vehicle to maintain a steady advancing movement even though the cutter vehicle has stopped to cut a tree. The boom assembly has pivot support which provides lateral positioning of the cutter vehicle to bypass a tree if desired. The cutter vehicle has a main frame which supports a vertically adjustable secondary frame having a lowered position for cutting a tree off adjacent the ground and a raised position for movement over the stump.