A device for comminuting whole trees or brush type vegetation comprising a set of more than two rotatable substantially horizontally oriented comminution drum assemblies said set of rotatable comminution drum assemblies being constructed and arranged in an angular orientation so that the uppermost rotatable comminution drum assembly in said set of more than two substantially horizontally oriented comminution drum assemblies first engages the top portion of the whole tree or brush type vegetation and the remaining rotatable comminution drum assemblies in said set of more than two substantially horizontally oriented comminution drum assemblies sequentially engage lower portions of the whole tree or brush type vegetation that exist immediately below the portions that are comminuted by each successive comminution drum assembly.
