Placing planter boxes on a fire escape is strongly discouraged and is often illegal. While the desire to add greenery to urban spaces is understandable, fire escapes serve one critical purpose: providing a safe and unobstructed path for emergency egress during a fire or other crisis. Planter boxes, along with furniture or grills, create dangerous obstacles that can block escape and hinder firefighter access. Their weight can also stress the structure, and watering can lead to slippery surfaces or water damage to the building.
Most local fire and building codes explicitly prohibit storing any items on a fire escape. Violations can result in fines. For safe urban gardening, consider secure window boxes, indoor plants, rooftop gardens (with permission), or community garden plots as excellent alternatives that keep your home and neighbors safe.