Under most leases, urban planter boxes are not automatically prohibited, but they are rarely covered by a blanket yes. Many standard lease clauses focus on damage, safety, common areas, and alterations, so a small, movable planter box placed inside the balcony is often acceptable if it does not create water damage, block drainage or exits, overload the structure, or become a nuisance. Fixed structures, rail-mounted boxes, large heavy planters, and irrigation changes usually need written landlord or HOA approval.
Because building rules can be stricter than the lease, check your agreement for terms such as alterations, balconies, water damage, fire safety, and nuisance. If the lease is silent, ask the landlord or property manager in writing before installing anything. Use lightweight containers, waterproof saucers, wind-safe placement, and avoid hanging planters over the railing or blocking emergency access.
If approval is required, describe the size, material, weight, drainage plan, and whether the boxes are movable. In short, most leases allow modest urban planter boxes on apartment balconies when they are lease-compliant, safe, and reversible; they are not a guaranteed right.