The entire lot, except for areas covered by buildings or surfaced as parking or service areas, shall be suitably landscaped. All front yards of properties adjacent to Marble Avenue shall be appropriately landscaped with trees, shrubs and lawn. Along property lines adjacent to Marble Avenue, there shall be planted street trees of such type, spacing and location as shall be approved by the Planning Commission of an initial caliper size of not less than 4 1/2 inches diameter at breast height (DBH). Where lot lines coincide with or are located within residence district boundaries, there shall be planted along such lines evergreen trees of such type and spacing as may be approved by the Planning Commission of an initial height of not less than five feet and adequate ultimately to screen all operations on the lot from the view of properties in the adjoining residence districts. At the discretion of the Planning Commission, an alternative type of buffer screening may be approved, provided that, in the judgment of the Planning Commission, it accomplishes the same purpose. Existing walls, trees or landscaping within 20 feet of any street or property line shall not be removed except with the approval of the Planning Commission, or as otherwise required in accordance with the provisions of § 185-43 of this chapter.