Urban planter boxes significantly benefit from being elevated off the ground, primarily to enhance air circulation around the root system. When planters sit directly on hard surfaces like concrete or decking, several issues can arise that compromise plant health.
Proper elevation creates crucial air movement beneath the container, preventing excess moisture accumulation that leads to root rot and fungal diseases. This airflow helps soil dry more evenly between watering cycles, mimicking natural ground conditions where earth breathes naturally. Many gardening experts recommend at least 1-2 inches of clearance, though taller elevations of 4-6 inches provide even better circulation.
The materials used for elevation matter significantly. Wooden blocks, brick stacks, or specially designed planter feet work well, while plastic or rubber spacers might trap moisture if not properly designed. Terracotta pot feet have been used for centuries specifically to address this need.
Beyond air circulation, elevation protects surfaces from water stains and prevents insects from easily accessing your plants. In urban environments where space is limited and surfaces are often artificial, this simple elevation technique can dramatically improve your gardening success. For concrete balconies particularly, elevation prevents the "heat sink" effect where hot surfaces cook container roots.
While not absolutely mandatory for all plants, elevation represents best practice for urban gardeners seeking thriving container gardens. The minimal effort required yields substantial returns in plant vitality and disease prevention.