Buffering is the provision of an area between different land uses that attempts to minimize negative environmental impacts from one to the other. Buffers shall provide a year-round visual screen in order to minimize adverse impacts. They may consist of fencing, evergreens, berms, rocks, boulders, mounds, or combinations thereof to achieve the same objectives. Every developer shall provide sufficient buffering when topographical or other barriers do not provide reasonable screening and when the Planning Commission determines that there is a need to shield neighboring properties from any adverse external effects of a development; or the development from negative impacts of adjacent uses such as streets or railroads. In high-density developments, when building design and siting do not provide privacy, the Planning Commission may require landscaping, fences, or to screen dwelling units for privacy. Buffers shall be measured from side and rear property lines, excluding driveways. Plant materials shall be sufficiently large and planted in such a fashion that a year-round screen at least eight (8) feet in height shall be produced within three (3) growing seasons. All plantings shall be installed according to accepted horticultural standards.