To ensure your wooden urban planter boxes last for many growing seasons, lining them is a crucial step. The primary goal is to create a barrier that protects the wood from constant moisture and soil contact, which are the main causes of rot. Here’s what you should use and how to do it effectively.
The most common and effective liner materials are heavy-duty plastic (like a pond liner or recycled plastic) and permeable landscape fabric. Plastic provides a complete waterproof barrier. When using plastic, always drill several drainage holes in the bottom of the planter box itself, *and then* also puncture holes in the plastic liner at the same locations to allow excess water to escape. Trapped water is worse than no liner at all.
Landscape fabric is a popular alternative as it blocks soil but allows water and air to pass through, promoting better drainage and root health. It's less effective at preventing moisture absorption than plastic but reduces the risk of waterlogging.
For the best protection, use a combination. First, apply a copper naphthenate-based wood preservative (safe for gardens) to the interior wood. Then, line the sides and bottom with plastic, ensuring proper drainage holes. Finally, add a layer of landscape fabric over the plastic to prevent soil from directly touching it and to wick moisture away from the wood.
Always use a layer of gravel or broken pottery at the bottom before adding soil to further improve drainage. Avoid lining only the sides, as the bottom is most vulnerable. With this simple lining process, you can significantly extend the life of your wooden planters and enjoy healthier plants.