Do I need to line my planter?

Deciding whether to put a liner in your planter depends on several factors, including the planter's material, the plants you’re growing, and the conditions where you will place the planter. Below are some key reasons for and against using a liner:

Reasons to Use a Planter Liner

1. Protecting the Planter Material
   Liners can protect metal planters (like Corten or galvanized steel) from water exposure, slowing down rust or corrosion. For wooden planters, a liner can help prevent rot by reducing direct contact with moisture.
2. Reducing Water Seepage
   If your planter has joints or seams, a liner can prevent water from seeping through, helping to maintain a tidy appearance and protecting surrounding surfaces.
3. Extending Planter Life
   A liner can add years to your planter’s lifespan by preventing soil and moisture from deteriorating the material, especially if it’s susceptible to damage from water exposure.
4. Soil Retention
   Liners can also help keep the soil contained, especially with planters that have gaps or minimal drainage systems.
5. Protection

You can use a liner to protect the powder-coated finish while other work continues around the edge.

Reasons Against Using a Planter Liner

1. Potential for Waterlogging
   Without proper drainage holes, a liner can trap water inside the planter, leading to waterlogging and root rot. It’s essential to allow excess water to drain away.
2. Reduced Natural Drainage
   For some plants, natural drainage through unlined planters can be beneficial. In certain cases, lining the planter may disrupt the natural moisture flow.
3. Aesthetic Preference
   Some prefer the natural weathering effect of materials like Corten steel or untreated wood, which can be part of the planter’s charm. A liner may reduce this effect. 

Water Seepage Through Panel Joints: What Are Your Options?

A common concern with metal planters is water seeping through the panel joints. Should this be a worry, and how can it be addressed? Here are some approaches to consider:

Using a Liner:

Using a GEO textile liner in your planter before adding soil is the best and most reliable way to ensure the longevity of your planter and prevent unsightly water leakage. Plastic liners can also be used successfully.

Do nothing:

In most instances, water seepage is not an issue at all.  While installing a liner is generally recommended, doing nothing has been successful in many projects.

Mastic Sealant:

Applying a mastic or silicone sealant between the panels is another practical solution. Mastic creates a flexible, durable seal that prevents water from seeping through the joints. This method is ideal for those looking to ensure their planter remains watertight over the long term.

Do Contain planters need drainage holes and a liner?

Contain planters are free standing standard sized planters with a steel base. They have drainage holes in the base to allow water to exit the planter. It’s recommended to place the planter on a porous surface to allow free-flowing water out of the planter.

Why Drainage Holes and a liner are Important:

The liner is important to stop any soil from washing away through the drainage holes in the bottom of the planter.

1. Preventing Waterlogging
   Without drainage holes, excess water has nowhere to escape, leading to waterlogged soil. This can suffocate plant roots by depriving them of oxygen, leading to root rot and ultimately killing the plants.
2. Controlling Soil Moisture
   Drainage holes help regulate the moisture levels in the soil. They allow excess water to flow out, ensuring that the soil remains moist but not overly saturated. This is particularly important if your planter is outdoors and exposed to rain.
3. Reducing Salt Buildup
   Over time, salts from fertilizers and tap water can accumulate in the soil. Drainage allows excess water to flush out these salts, preventing them from building up and damaging your plants.

When Drainage Holes and Liner May Not Be Necessary

Using a Liner with Drainage Control: Some planters use a liner with controlled drainage systems, like self-watering planters, which allow excess water to be stored and absorbed as needed. In these cases, drainage holes may not be essential.

Indoor Planters with Saucers: If your planter is indoors, you can place a saucer under the planter to catch excess water. However, even in these cases, drainage holes are recommended to prevent water from stagnating at the bottom.

Open-based planter systems: most raised beds and larger planters are open-based meaning that any moisture can drain into the ground on which the planter is installed.

Conclusion:

You should now have a better idea of what a liner is for and when you should use one. Usually, it is best to use a liner for control of water exiting the planter whilst retaining the soil. In raised bed situations, a liner is not necessary.

The risk of water, causing issues weeping through panel joints is low. Joints are tight and any water on the planter's face is likely coming from outside, rather than inside the planter.  Additionally, if the planter drains well, water will naturally flow vertically rather than horizontally between two tight side returns.

In general, if your planter has a base, it’s best to have drainage holes and a liner, to keep your plants healthy, especially for most outdoor and traditional container gardening setups.  If your planter has an open base, water will naturally drain through the liner into the subsoil.