When installing planter boxes in urban settings, a special base or support system is highly recommended rather than placing them directly on pavement. Direct contact can lead to several issues. Most importantly, it blocks drainage holes, causing waterlogging and root rot. The constant moisture trapped underneath can also stain and degrade pavement surfaces over time. Furthermore, direct placement limits air circulation to the bottom of the planter and can make the box unstable.
The ideal solution is to use a raised base or feet. This creates a crucial air gap for drainage and ventilation. You can use purpose-built planter stands, simple wooden battens, or plastic feet. For larger or permanent installations, a gravel or permeable base layer is excellent. This setup protects both your plants and the public infrastructure. Always ensure your planter has sufficient drainage holes, and consider using a permeable landscape fabric liner to contain soil while allowing water to escape. This approach ensures healthy plant growth and preserves the integrity of the sidewalk.