A landscaped buffer shall consist of evergreen trees, planted at least 12 feet on center, at a minimum height of six to eight feet when planted; evergreen shrubs, at a minimum size of 2.5 to three feet when planted; and deciduous shrubs, at a minimum size of two to three feet when planted. The Planning Board, when considering a site plan, may require the buffer to be enhanced by berms, fences or walls to provide an effective screen with neighboring residential uses.