For successful urban gardening in planter boxes, a high-quality, well-draining soil mix is non-negotiable. Standard garden soil compacts easily in containers, leading to poor root growth and waterlogging. The ideal blend is a soilless potting mix, often called a "container mix," which provides the perfect structure for roots to thrive in a confined space.
I recommend a simple, effective recipe: combine 60% high-quality potting mix (a peat-based or coconut coir blend) with 30% compost for nutrients and microbial life. For the final 10%, add coarse horticultural sand or perlite to ensure excellent drainage and aeration. This combination prevents compaction, retains moisture without becoming soggy, and provides a steady supply of organic nutrients.
Always fill your planter boxes completely with this mix, watering thoroughly after planting. Remember, the right soil foundation is the key to vibrant flowers, robust herbs, and productive vegetables on your balcony, patio, or rooftop.