The short answer is maybe, but you should assume no until you have written permission. A fire escape is not a normal balcony or decorative ledge; it is an emergency exit. Many landlords, building managers, and local fire codes prohibit storing objects there because planters can block escape routes, create tripping hazards, add unexpected weight, or become dangerous in high winds. Even a small urban planter box can raise liability concerns if it interferes with emergency access or damages the building.
Your lease may also have rules about modifications, outdoor planters, drainage, and use of common areas. Some leases specifically prohibit using fire escapes for storage or personal items, and violations can lead to fines or lease issues. The landlord’s insurance policy may also have requirements about obstructions and fire safety.
The best approach is to ask your landlord in writing before buying or installing anything. Be specific: share the planter’s dimensions, weight, material, how it will be secured, and how you will prevent water damage and blockage. Ask whether the building has any written fire escape policy. If the landlord says yes, get that approval in writing and follow all safety limits. Keep the path completely clear, use lightweight and non-combustible materials, secure the planter against wind, and never let vines or pots hang over the railing.
If the answer is no, consider safer alternatives such as a proper balcony railing planter, a window box designed for your building, indoor containers, a shared courtyard, or a community garden. Your landlord may be more open to an urban planter box in an approved outdoor area than on the fire escape. In short, do not install it first and ask later. Ask first, get written permission, and prioritize fire safety and your lease. When in doubt, check with your landlord, building manager, or local fire department.