When setting up an urban planter box, a common question arises: is a special liner necessary before adding soil? The answer isn't a simple yes or no; it depends on your box's material and your gardening goals.
Primarily, a liner serves two key functions: protecting the planter material and managing soil and moisture. For wooden planter boxes, a liner is highly recommended. It acts as a barrier between the damp soil and the wood, significantly slowing rot and decay, thereby extending the planter's lifespan. Without it, constant moisture will cause the wood to deteriorate quickly.
For metal or concrete planters, a liner can prevent soil stains and, in the case of certain metals, mitigate potential corrosion from constant dampness. Plastic or fiberglass planters are often inherently water-resistant and may not require an additional liner for protection.
The second critical role is drainage control. A liner should never be completely impermeable. The goal is to protect the structure while still allowing excess water to escape. Always ensure your planter box has adequate drainage holes at the bottom. When using a liner, such as a landscape fabric or a perforated plastic sheet, place it *inside* the box, covering the holes but not clogging them. This allows water to drain while keeping soil in.
A good practice is to add a drainage layer of coarse gravel or pebbles at the bottom before adding your soil. This creates space for excess water to pool away from plant roots, preventing waterlogging.
In summary, while not always absolutely mandatory, using a breathable, drainage-friendly liner is a wise investment for most urban planter boxes. It protects your investment, promotes healthy plant growth by preventing root rot, and makes for a more manageable and durable container garden. For wooden boxes, it's essential. Choose materials like landscape fabric or perforated polyethylene that offer protection without sacrificing proper drainage.