Unenclosed uses. Any use which is not conducted within a completely enclosed building, except for nurseries, and the display for sales purposes of new or used cars, trucks, trailers or farm equipment, in operative condition, shall be entirely enclosed by a fence maintained in good condition or evergreen-type hedges or shrubs spaced at intervals of not more than six feet. The evergreens, hedges or shrubs which make up this visual screen shall be at least six feet high at the time of planting. They shall also contain foliage year-round which will measure at least four feet in diameter for the first six feet above the level of the ground.