Filling multiple large urban planter boxes with soil can seem daunting and expensive. However, with a strategic approach, you can achieve a lush garden without breaking the bank. The most cost-effective method is to use a layered filling system combined with bulk material sourcing.
First, do not fill the entire box with premium potting mix. Instead, create a filler layer at the bottom. Use clean, broken polystyrene packaging, empty plastic bottles (capped), or upside-down plastic pots to occupy volume. This improves drainage and reduces soil needed by 30-50%.
Next, source your soil in bulk. Contact local landscape supply companies for delivery of a high-quality topsoil and compost blend. Buying by the cubic yard is vastly cheaper than bags. For even greater savings, create your own mix by purchasing bulk topsoil and separately buying compost or well-rotted manure to blend in a 70:30 ratio.
The key layers from bottom to top are: 1) Drainage filler (polystyrene/pots), 2) A layer of coarse sand or fine gravel for drainage, 3) Bulk topsoil-compost mix, and 4) A final top layer of premium potting mix or enriched compost for planting.
This method ensures healthy root growth and proper drainage while minimizing cost. Always check soil quality; cheap soil must still be free of contaminants and weeds. For very deep boxes, consider a "false bottom" using landscape fabric over the filler layer to prevent soil from washing down. By planning and using bulk materials, you can sustainably and affordably fill all your urban planters.