That's an excellent question for any urban gardener looking to combine style with practicality. The short answer is yes, high-quality felt planter boxes are surprisingly durable for outdoor use, but their longevity depends on several key factors.
Modern felt planters are typically made from non-woven polypropylene fabric, which is UV-stabilized and designed to withstand the elements. Unlike traditional clay or ceramic pots, they are flexible, breathable, and promote "air-pruning" of roots, leading to healthier plants. Their durability outdoors hinges on the felt's thickness (measured in grams per square meter, or GSM), the quality of the UV inhibitors, and your local climate.
For best results, place them in a location with some protection from the harshest afternoon sun, which can accelerate fabric breakdown over many seasons. They are naturally drainage-friendly, preventing waterlogging. While they may develop a patina of moss or show slight fading after a few years—adding to their rustic charm—a quality planter can easily last 3-5 seasons or more with proper care. To maximize their life, avoid dragging them across rough surfaces and empty them during freezing winters to prevent ice from stressing the fabric. For urban balconies, rooftops, and patios, they offer a lightweight, durable, and plant-healthy solution.