Within the required buffer areas, a solid and continuous landscape screen shall be planted and maintained. Said landscaping shall consist of massed evergreen and shrubs or a combination of evergreens, shrubs and deciduous trees. Deciduous trees shall have at least a two-inch caliper at planting. Size of evergreens and shrubs shall be allowed to vary depending on setting and type of shrub. Only nursery-grown plant materials shall be acceptable; and all trees, shrubs and ground covers shall be planted according to acceptable horticultural standards. The buffer is to be planted so as to continually restrict a clear view beyond said buffer strip, provided that such planted strip shall be located within the buffer strip furthest from the adjacent residential district. The portion of any naturally forested buffer strip that does not need to be cleared to establish a "solid and continuous landscape screen" should be left undisturbed.