Whether you need a liner for your urban planter box depends primarily on the box's material and your gardening goals. For wooden planters, a liner is highly recommended. Planting directly in untreated wood exposes it to constant moisture and soil, accelerating rot and decay. A durable plastic or landscape fabric liner acts as a protective barrier, significantly extending the planter's lifespan. It also helps contain the soil and prevents staining from drainage water. However, ensure your liner has or allows for adequate drainage holes to prevent waterlogged roots.
You can plant directly in planter boxes made from more resilient materials like metal, fiberglass, or certain plastics. These materials are less susceptible to water damage. The key consideration then becomes drainage. Always check that there are sufficient holes in the bottom. To improve drainage and prevent soil from washing out, add a layer of coarse gravel or broken pottery shards at the base before adding soil.
Using a liner offers control and protection, while planting directly can simplify the process. For long-term use, especially with wooden boxes, installing a liner is a wise investment. For temporary or durable non-porous planters, direct planting is a perfectly viable option. Always prioritize good drainage for healthy plant growth in any urban container garden.