Yes, urban planter boxes absolutely need holes in the bottom. Drainage is a non-negotiable element for healthy container gardening in cities. Without an escape route, excess water accumulates at the root zone, creating a waterlogged environment. This suffocates plant roots by depriving them of oxygen and leads to fatal root rot. While it may seem counterintuitive when trying to keep plants hydrated, proper drainage is what allows for a balance of air and water in the soil.
For urban settings like balconies or rooftops, drainage holes also prevent heavy containers from becoming waterlogged and excessively weighty. If your chosen decorative box lacks holes, you have options. You can drill them yourself using an appropriate bit for the material. Alternatively, use the box as a cachepot: place a smaller, perforated nursery pot inside it, ensuring the inner pot is elevated so water can drain freely into the outer container without the roots sitting in it. A layer of gravel at the bottom without holes is a common but ineffective myth; it simply raises the water table inside the pot. Prioritizing drainage is the key to thriving plants in any urban garden.