Yes—climbing beans can work well in an urban planter box with a small trellis, provided you treat the trellis as a real structural support and choose varieties that match the space. The main limitations are soil depth, trellis height, wind, and watering consistency, not the planter box concept itself.
Start with a planter at least 30–40 cm deep and 45–60 cm wide, with drainage holes. Climbing beans develop a deeper root system than many herbs or lettuce, so shallow balcony boxes dry out too fast and limit yield. Use a rich, well-draining potting mix and add compost. Space plants about 15–20 cm apart; in a small box, that usually means two to three plants, not a dense row. More plants will compete for light, water, and trellis room.
A small trellis can be enough if it is stable. Aim for 1.2–1.8 m if possible, and attach it firmly to the planter, wall, or railing rather than relying on a loose frame. Climbing beans can become top-heavy and catch wind on a balcony, so secure the box and use soft ties when needed. If your trellis is shorter, choose compact climbing varieties, pinch out the growing tips when vines reach the top, and keep vines guided across the trellis instead of letting them sprawl. In very small spaces, bush beans may be more practical, but climbing beans are still possible.
Give them full sun—at least six hours, ideally more—and consistent moisture. Water when the top few centimeters of soil feel dry, but avoid soggy soil. Mulch helps moderate moisture in urban containers. Feed lightly with a balanced fertilizer; too much nitrogen encourages leaves rather than pods. Protect young plants from strong wind and check the trellis after storms.
With reasonable care, you can harvest fresh beans from an urban planter box. Pick pods regularly to keep plants producing, and watch for aphids, spider mites, and slugs in sheltered balcony conditions. So yes: a small trellis is not a deal-breaker—it just means choosing compact beans, securing the setup, and staying realistic about yield.