When setting up an urban garden, a common question arises: do planter boxes need a liner, or is the material itself waterproof? The answer isn't a simple yes or no; it depends on the material of your planter box and your goals for plant health and container longevity.
Most planter box materials are not inherently waterproof. Wood, a popular choice for its aesthetic, is porous and will rot over time when constantly exposed to soil and water. Metal planters, like galvanized steel, can eventually rust. Concrete and terracotta are also porous, allowing water to seep through. For these materials, a liner is not just recommended; it's essential. A liner acts as a protective barrier, preventing water from damaging the box and extending its life dramatically.
However, some modern planters are made from waterproof materials like high-quality, UV-stabilized plastic, fiberglass, or powder-coated metals. These are designed to hold water without a separate liner. Even with these, the primary concern shifts from waterproofing to drainage. Without proper drainage holes, water will accumulate at the bottom, leading to root rot and killing your plants.
So, what is the true purpose of a liner? Its main job is to protect the container, not to hold water in. It shields the planter material from constant moisture and the corrosive elements in soil. For drainage, you must ensure there are holes in the bottom of the planter box or its liner. A good setup involves a waterproof liner with pre-drilled drainage holes inside a decorative, non-waterproof outer box.
In conclusion, while a few planter boxes are waterproof, most are not. Using a liner is a best practice for protecting your investment. Always prioritize a system that includes both a protective barrier and excellent drainage for a thriving urban garden.