Yes, you can use an urban planter box to grow a privacy hedge on a terrace, but the planter must be treated as a small-scale growing system rather than a decorative pot. For a hedge that actually screens the terrace, choose a long trough or modular planter boxes at least 45–60 cm deep and wide enough for the mature root ball; shallow, narrow boxes dry out too quickly and restrict growth. Use a lightweight, free-draining soil mix, add drainage holes and a gravel or geotextile drainage layer, and make sure the terrace structure can carry the weight of soil, plants, water, and winter saturation. Secure the planter and hedge against wind, especially on upper floors, and consider a trellis or tension wires for extra stability.
Plant selection matters more than planter style. Choose compact, slow-growing, climate-appropriate shrubs that tolerate container life and pruning, such as boxwood, privet, photinia, or clumping bamboo where conditions allow. Avoid vigorous or invasive species, and check local rules for terrace structures and plant height. Install drip irrigation with a timer, because planter hedges dry out faster than garden beds, and prune regularly to keep the hedge dense and within bounds. With a deep, stable planter, reliable irrigation, and the right plants, an urban planter box can create effective privacy on a terrace—but it will need more watering, feeding, and root management than an in-ground hedge.