Urban planter boxes bring greenery to city spaces, but a common concern is whether they need a special liner to prevent rot. The short answer is: it's highly recommended and often essential for longevity. While not always an absolute requirement, a proper liner serves as a critical barrier between moist soil and the planter's inner walls, significantly slowing the decay process, especially in wooden boxes.
The primary threat to planter boxes is constant moisture exposure. Soil and water retained against the interior surface create a perfect environment for wood rot and can accelerate corrosion in metal. A liner mitigates this by providing a waterproof shield. It's crucial, however, that any liner works in tandem with excellent drainage. Liners should have pre-cut holes aligned with the planter's drainage holes to prevent water from pooling at the bottom, which can lead to root rot and structural damage.
For material selection, consider durable, flexible pond liners or heavy-duty plastic sheeting. Avoid using non-porous materials like solid rubber or impermeable plastics without adequate drainage modifications, as they can suffocate roots. Some gardeners use landscape fabric, which allows moisture and air exchange while protecting the wood, though it may break down over time.
Ultimately, investing in a suitable liner is a simple, cost-effective step. It extends the life of your planter box dramatically, protects your plants from harmful waterlogging, and reduces long-term maintenance, making your urban gardening project more sustainable and enjoyable.