Short answer: maybe—and sometimes yes. I can’t give you a definite yes or no for “where I live” without knowing your city, country, and exactly where the planter box will go, because rules vary a lot from one place to another. In many urban areas, a planter box on private property—such as a backyard, courtyard, or private patio—usually does not need a permit if it is small, movable, and not attached to a structure. But if it is tall, heavy, built-in, on a roof or balcony, or part of a fence, wall, or deck, permits or structural checks may apply.
The biggest dividing line is usually public versus private property. If the planter box will sit on a sidewalk, curb zone, street, plaza, alley, or other public right-of-way, many cities require some kind of permit, encroachment agreement, sidewalk-use license, insurance, or design approval. Even where permits are not required, there may be rules about clear pedestrian access, fire hydrants, bus stops, loading zones, sight lines, utility access, drainage, and accessibility for wheelchairs and strollers. A planter box that looks harmless can become a problem if it blocks a required path or creates a tripping hazard.
You should also check local zoning and building codes. Some places regulate front-yard landscaping, setbacks, height limits, fence-like structures, historic districts, and design standards. If you rent, your lease may ban or restrict planter boxes. If you live in an HOA, co-op, condo, or managed building, private rules may be stricter than city rules. Fire codes matter too: don’t block exits, fire lanes, standpipes, or emergency access. On balconies and roofs, wind load, waterproofing, drainage, and weight can be serious issues, and building permits may be needed for larger or attached installations.
The safest way to find out is to contact your local planning, zoning, buildings, or public works department before you buy or install anything. You can ask a simple question: “I want to place a planter box at [address or location]. Does it need a permit, and are there setback, right-of-way, fire, accessibility, or design rules?” If it is going on a sidewalk or street, ask specifically about a right-of-way or sidewalk encroachment permit. If you rent or live in an HOA, ask your landlord or building manager as well. This is not legal advice, but as a practical rule: check first, keep the box movable and clear of paths, and get written confirmation if the location is even slightly public or shared.