Industrial A screening. In an Industrial A District, trees, shrubbery or grass shall be maintained on a strip not less than 20 feet wide along all public roads bounding the lot, and trees and shrubbery shall be maintained on a strip not less than 50 feet wide along all lot lines adjacent to residential districts, except strips used for entrance drives or entrance walks. All open storage must be adequately shielded or covered by a wall, fence, shrubbery or natural vegetation.