For thriving herbs and small vegetables in urban settings, the depth of your planter boxes is crucial. Most popular herbs like basil, cilantro, thyme, and chives, along with compact vegetables such as lettuce, radishes, and green onions, require a soil depth of 6 to 12 inches (15 to 30 cm). This range provides adequate space for root development, moisture retention, and nutrient access.
Deeper boxes, around 12 inches, offer more flexibility and buffer against drying out, which is beneficial for heartier small veggies like dwarf kale or bush beans. Ensure your containers have sufficient drainage holes to prevent waterlogged soil, a common issue in shallow planters. For a mixed planter, aim for the 12-inch depth to accommodate the varying needs of different plants. Using a quality potting mix, rather than garden soil, is essential for proper aeration and drainage in these confined spaces. With the right depth and care, your urban planter can yield a continuous, fresh harvest.