A planter box is a blessing to grow my favorite plants on my apartment balcony. But I wanted to find out whether I need to line my planter box before use.

You need to line your planter box if it’s made from wood or metal. The liner will help prolong the planter’s life. You don’t need to use a liner if the planter is made using plastic, ceramic, or concrete as they are quite durable by themselves.

I’ve written details below that will help you understand more about using a liner for your planter box. You’ll find information about the different types of materials and what I recommend. I’ll also show you how to use the liner in your planter box.

When should you use a liner for your planter box?

I would recommend that you use a liner when your planter box is made of organic material like wood. The material will degrade over time. But moisture from the soil will speed up the process.

If you put the potting soil in a wooden planter and keep watering it, the moisture will decay the wood. You may need to replace the planter box every year if that happens.

There will be beneficial organisms in the soil that will break down the wooden material and also increase the rate at which the planter box will decay.

The other time you may need to use a liner is if your planter box is just a wireframe. You may find that a hanging basket comes with such a wireframe and there is typically a coco coir liner to hold the potting soil.

What material can you use as a liner?

I would suggest using a plastic bag or sheet as a liner if your planter box is made from wood or metal.

Plastic is the only material that is not permeable. So it will not leach out water into the wooden planter causing it to rot. If you use a metal planter, it may rust due to the moisture. Plastic is also very durable and will last a long time in your planter box.

You can also use a plastic pot to grow the plant and place the pot inside your planter box. You’ll still need to line the planter box with plastic. This helps protect the planter material from the water that drains out of the plastic pot.

Using a plastic pot inside the planter box will help you plant new seedlings with ease. It also makes it easier to replace the liner by just moving the pots out of the planter box.

If you’re using a hanging basket made with a metal wireframe, you have a lot more options to choose from. You can use landscaping fabric, burlap, coco coir, sphagnum moss, newspaper, and even old jeans.

Liner materialSuitable forProsCons
Coconut fiberWireframe planterGood drainage It’s a natural material Looks attractiveExpensive Need to buy from a specialty store
Landscape fabricWireframe planterGood drainage Easy to install Keeps the soil in wellMade from synthetic material Average looking
A plant potWireframe planter Metal planter Wooden planterEasy to install Allows no dirt through itPoor drainage Average looking
Plastic linersWireframe planter Metal planter Wooden planterEasy to find around the home Easy to install Lasts a long time Good drainage if holes are usedNot the best looking Is made of synthetic materials
Sphagnum mossWireframe planterLast for a few years Good drainage Organic materialExpensive Not sustainable

How can you use the liner in your planter box?

I will show you the steps you can use to line your wooden or metal planter box with a plastic liner. You can use any plastic bag like a garbage bag or a plastic sheet.

You should first clean the planter box well before using the liner. Mix 1 part bleach with 9 parts water in a sprayer.

Spray all the inner parts of the planter box to sterilize it. The mix will remove any unwanted pests and diseases from the planter. Let the mix stay on the planter box for at least an hour.

You can then flush the mix using clean water. Let the planter box dry before you can add the liner.

You should drill a few holes in the bottom of the planter box to allow for drainage. The holes can be 1/4th inches in diameter.

I recommend coating the outside of the planter box with a varnish that will protect it. You can apply a coat and let it stay for a day. Then apply a second coat of the varnish. Apply the varnish inside the drainage holes as well.

You should apply a coat of waterproofing liquid on the insides of the planter box. Let it dry for a day and you can apply a second coat.

You will use a plastic liner but moisture can still seep between the liner and the planter material. The waterproofing liquid will ensure that moisture does not harm the planter box.

The next step would be to use a wood sealer on all the inner edges of the planter box. This wooden sealer will prevent the soil and moisture from seeping into the edges.

Now you can place the plastic liner inside the planter box. You can use a double layer to give more protection. If the plastic liner is larger than the planter, you can cut it so it fits inside it.

Fasten the plastic liner to the sides of the planter box using clips. Use a screwdriver or knife to make holes in the plastic at the places where you have drilled drainage holes in the planter.

Pour the potting soil inside the planter until just 1-2 inches remain from the top. Now you can remove the clips as the potting soil will hold the plastic liner inside the planter box.