With off-street parking for four or more cars, excluding single-width driveways, all lots shall be provided with at least a five-foot wide buffer strip in the required side and rear yards and on which no impervious cover is allowed. The buffer area must be provided with a permanent landscape screen of trees and shrubs and/or fencing. The purpose of the screen is to block any view of the off-street parking lot from the street, other than along a driveway, and from all abutting residential properties. Landscape plans shall include a minimum of 60% evergreen material. The shrubs shall be a minimum of three feet in height at the time of planting and have a mature height of at least five feet. Evergreen trees shall be at least five feet in height at the time of planting and must be accompanied by low-growing material to supplement the screen when these trees are mature and have a tendency to lose lower branches. Deciduous trees shall have a caliper of at least 2 1/2 inches in diameter, measured four feet above the ground.