The best way to arrange multiple urban planter boxes on a small deck for privacy is to treat them as a layered privacy system rather than as separate containers. Start by standing at the main seating area and looking outward. Mark the sightlines you most want to block, such as a neighboring window, a street, or a nearby balcony. Place the tallest, densest planter boxes along those lines, preferably in an L-shaped or U-shaped layout around the deck edge. This creates a soft green screen without making the deck feel boxed in.
Stagger the heights of the planter boxes instead of lining up identical containers in a flat row. Use tall boxes at the corners and lower boxes between them, or set some planters on sturdy, level risers where weight and safety allow. A mix of heights looks more natural and blocks more angles of view. Leave small gaps between boxes for airflow, light, and easy access to watering. Do not pack the perimeter so tightly that the deck feels cramped or blocks an exit, railing, drain, or utility access.
Choose plants that suit the screen function: upright evergreens, ornamental grasses, bamboo in contained planters, or dense flowering shrubs. Evergreen plants are especially useful because they provide year-round privacy. Match plant size to box size, and avoid plants that will quickly outgrow the space. On a small deck, a few well-planted boxes with tall, dense growth usually work better than many small pots with low plants.
Weight, drainage, and wind matter. Place the heaviest boxes over structural supports or near load-bearing edges, and confirm that the deck can handle the combined weight of soil, plants, and water. Use saucers or drainage trays to protect the deck surface. In windy urban settings, anchor tall planters or use interlocking bases, and keep the heaviest boxes low if stability is uncertain. Finally, arrange the boxes to create a gentle sense of enclosure around the seating zone rather than a solid wall. A curved or staggered line, with taller planting at the exposed side and lower planting near the entrance, gives privacy while preserving light, ventilation, and comfortable movement.