How to Line a Planter Box | Soil Stays, Wood Lasts

Lining a planter box involves measuring the interior, cutting liner material with extra overlap, securing it to the sides, and aligning drainage holes with the box’s openings — a process that takes under an hour and dramatically extends the life of wooden planters.

A planter box without a liner is a planter box rotting from the inside out. Moisture trapped against wood accelerates decay, and soil washing out of drainage holes makes a mess of your patio. Lining changes both problems with one simple barrier. Whether you are building a cedar box for vegetables or reviving a thrifted metal planter, the same core method works — and knowing which materials to avoid saves you from redoing it next season.

How To Line A Planter Box: The Sequence That Works

Start with a clean, dry box. Wash the interior with hot soapy water and let it dry completely. If the box is wood, apply a plant-safe waterproofing sealer before installing any liner — skip this on plastic, ceramic, or metal boxes, where waterproofing does nothing.

Measure the interior length, width, and depth. To get the right liner size, add double the depth to both the length and the width. That extra material will wrap over the top edges and stay in place when you secure it. Cut your liner to those dimensions, then lay it loosely inside the box. Do not pull it tight — tight liners tear when soil expands after watering.

Secure the liner at the top edges. For wooden boxes, use staples or tacks. For metal or plastic, use adhesive or glue. If you are working with a planter that does not have drainage holes, drill them through the bottom of the box first, then pierce matching holes through the liner in the same spots. Misaligned holes defeat the whole purpose. Trim the excess liner, leaving roughly one inch above the soil line as a barrier against splash and surface moisture.

For better drainage, place a layer of landscape fabric, geotextile fabric, gravel, screen cloth, or broken pottery over the bottom before adding soil. If you’re choosing between materials for long-term durability, our tested roundup of landscape fabrics for planter boxes compares permeability, lifespan, and how well each stays put under heavy soil.

Which Liners Work — And Which Do Not

Not every liner belongs in every box. Plastic sheeting and pond liner are the most effective moisture barriers, but they must be pierced for drainage because they trap water completely. Landscape fabric and geotextile fabric let water pass while holding soil in place, which makes them a better choice for planters that get heavy rain. Coir and coconut fiber look natural and breathe well, but they break down after one or two seasons and need replacement. Screen cloth is a fine bottom-layer solution for keeping drainage holes open.

The common mistake is cutting the liner too small or pulling it tight — both guarantee tears when the soil settles. Another frequent error is forgetting to align drainage holes, which creates a sealed basin that drowns roots. Staples work for wood; adhesive works for metal and plastic. Using the wrong fastener for the box material just creates extra work.

When Lining Matters — And When It Does Not

Wood planter boxes benefit the most from lining. The barrier reduces moisture contact with the wood and slows rot significantly, especially if you sealed the wood first. Metal planters also need lining because moisture accelerates rust from the inside. For plastic, ceramic, concrete, stone, or terracotta planters, lining is usually unnecessary — these materials do not degrade from moisture, and the liner can actually trap water against the roots if drainage is poorly managed. If you line a non-porous planter, pierce the liner generously and check that water flows freely within a few seconds of watering.