A window box planter is a rectangular container designed to be mounted along windowsills, railings, fences, or deck rails to display flowers, herbs, trailing vines, or other plants. These planters bring greenery and color to small spaces where traditional garden beds are not practical, making them ideal for balconies, patios, and front entrances.

Window box planters typically feature drainage holes to prevent waterlogging, durable weather-resistant construction suitable for outdoor year-round use, and a classic elongated profile that fits standard window widths. Many models include mounting hardware or integrated brackets for secure attachment to horizontal surfaces, while others can simply rest on wide ledges or sills.