Selecting the right soil is crucial for the success of your urban garden. For planter boxes and raised beds, avoid using dense garden soil from the ground, as it compacts easily and drains poorly in containers. The best choice is a high-quality soilless potting mix. These blends typically contain ingredients like peat moss or coconut coir, pine bark, perlite, and vermiculite. This combination provides excellent drainage, aeration, and moisture retention—preventing both waterlogging and rapid drying out.
For edible plants, enrich a basic potting mix by adding compost or well-rotted manure (about 25-30% of the total volume). This adds essential nutrients and improves soil structure. If you are filling deep boxes, a "lasagna" method can save mix: place a layer of clean, broken pottery or small rocks at the very bottom for extra drainage, then fill the bottom third with cheaper materials like untreated wood chips or leaves, and use your premium potting mix-compost blend for the top two-thirds where the roots will grow.
Remember, container soil gets depleted. Refresh it each season by topping off with compost and a balanced, slow-release organic fertilizer to keep your plants thriving in the city.