Absolutely! Using a liner in your urban planter boxes is not only acceptable but highly recommended. A liner acts as a protective barrier between the moist soil and the planter material (often wood), preventing rot, extending the planter's lifespan, and helping to retain soil. The key is choosing a liner that allows for proper drainage to avoid waterlogged roots.
For most wooden planter boxes, a durable geotextile fabric (landscape cloth) is often the best choice. It is permeable, allowing excess water to drain while containing the soil. Alternatively, a perforated plastic liner (like a heavy-duty pond liner or plastic sheeting with holes poked in the bottom) works well, especially for metal planters where you want to prevent rust. Avoid non-porous materials without drainage holes, as they will cause root rot.
Here’s a simple approach: Line the interior with your chosen material, ensuring it covers all sides. Secure it with staples or tacks for wood planters. Crucially, puncture or cut several drainage holes in the bottom liner layer before adding a 1-2 inch layer of gravel or broken pottery. Then, add your soil. This setup protects your box, manages moisture, and creates a healthy environment for your plants to thrive in the city.