Adding a liner to your wooden urban planter box is highly recommended. It acts as a crucial barrier, protecting the wood from constant moisture and soil contact, which prevents rot and significantly extends the life of your planter. The right liner also helps retain soil and prevents it from washing out through drainage holes.
For most situations, a breathable, permeable landscape fabric is an excellent choice. It allows water to drain freely, preventing soggy soil and root rot, while blocking soil from escaping. Simply line the interior sides and bottom before adding soil.
Other common options include durable plastic sheets (like pond liner) with pre-punched drainage holes. Avoid non-porous plastic without holes, as it causes waterlogging. For a natural look, consider coconut coir or burlap liners, though they decompose over time and need replacement.
Regardless of your liner choice, ensure your planter box has adequate drainage holes at the bottom. A layer of gravel or pebbles beneath the liner can further improve drainage. This simple step of using a liner will keep your wooden planters healthy and beautiful for many growing seasons to come.