All developments or enlargements shall provide and maintain trees of not less than three-inch caliper at the time of planting in the sidewalk adjacent to the building on the side of the sidewalk closest to the travel lane. All such trees shall be provided for the entire length of the frontage of the building, for every 25 feet of such frontage, except where curb cuts or utilities make such planting infeasible. Species shall be selected, installed and maintained in accordance with specifications established by the Department of Parks and Recreation. However, street trees need not be provided where such trees may interfere with truck movements in the loading area for a convention center.