That's an excellent question for any city gardener looking to simplify their routine. The good news is that most modern urban planter boxes are designed for low maintenance, but the answer depends heavily on the material.
For classic wooden planters, some periodic care is recommended. Applying a natural, non-toxic wood oil or sealant every year or two can significantly extend their life by protecting against moisture rot and weathering. This isn't strictly mandatory, but it prevents warping and fading.
Conversely, planters made from powder-coated metal, composite wood, fiberglass, or high-quality plastic typically require no such treatment. These materials are engineered to withstand the elements without sealing or oiling. Their maintenance usually just involves occasional cleaning with soap and water to remove dirt and mineral deposits.
The universal key for all planter boxes is proper drainage. Ensure drain holes are never clogged to prevent waterlogging, which is the primary cause of damage. Beyond that, your maintenance focus should be on the plants themselves—watering, feeding, and pruning. Choosing a planter made from a durable, modern material from the start is the easiest path to a care-free urban garden.