What is a tree box?

Tree boxes are a green infrastructure stormwater control measure that is designed to collect the first storm water discharge and treat it before discharging it to the storm sewer system or underground. A tree-shaped filter is one of the best management practices (BMP) or a stormwater treatment system that is widely implemented on sidewalks, street curbs, and car parks. They are used to control the volume and amount of pollutants from urban runoff that enter local waters, providing areas where water can accumulate and infiltrate or naturally seep into the ground. These systems usually consist of a tree planted in a soil substrate, contained in a small, square concrete box.

Tree box filters are popular bioretention and infiltration practices, as they collect, retain and filter runoff as it passes through vegetation and soil microorganisms. The tree then consumes the water or transfers it to the storm drain system.