We all want to make our gardens look as beautiful as possible but not everyone has the capacity to plant in the ground so using planters and containers is a great alternative. These decorative boxes give you space to grow a whole host of plants, flowers, and veggies but when you get ones that are quite large, filling them with only potting soil can be very expensive. Fortunately, there are several innovative ways that you can fill your wooden planter box without breaking the bank. Foam balls, pop bottles and even old rubble are all viable ways to fill a planter. In this guide, we will be taking a more in-depth look at how to fill a wooden planter box, saving you money and still providing an environment for healthy, happy plants.

Wooden planter box
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Is Wood a Good Material for a Planter Box?

Yes, wood is a very good material for a planter box and is among the most popular. What’s even better is that it’s entirely possible for you to build a wooden planter yourself using leftover material from other projects, further lowering the cost. Of course, as with anything, there are drawbacks to using wood to make planters and this includes their correct preparation. Failing to do this will result in it not lasting as long as it should. If you can’t afford to buy a planter, we have written instructions for how to build one yourself.

How To Fill A Wooden Planter Box

There are many things you can use to fill a large wooden planter as opposed to just ramming it with potting soil. This can get very expensive but what a lot of people don’t realise is that they already have an array of items already lying around their home!

What You Need

  • Plastic liner
  • Filler Material (such as rubble etc.)
  • High-quality potting soil
  • Well-rotted manure or fertiliser
  • Plants, flowers, or seeds

Step 1 – Line with Plastic

We would recommend using a plastic liner that is 100% waterproof as this will stop moisture from getting into contact with the wood which can cause it to deteriorate and rot.

Planter Liner
Planter Liner

These liners can be stapled to the container or held in place using wood glue. Once you’ve installed one, you’re ready to start filling your container with soil and other items.

Step 2 – Bulk Out with Filler

If you have a rather large planter and you are only using it for flowers and not large root vegetables, you will want to add some filler.

Tall Planters May Need to be Part Filled
Tall Planters May Need to be Part Filled

Adding filler will reduce the need for as much soil and depending on what you use, it will keep the weight down to prevent the wooden structure from warping. Just remember to leave 6-8 inches for the topsoil.

What to Use to Fill the Bottom of a Planter?

1 – Foam

In modern times, we are all guilty of ordering way too much online but one of the advantages of this is that we’re left with lots of foam balls. These are ideal for use in a wooden planter to fill up space before adding your soil. Another option here is to use blocks of foam but whichever method you choose, it is highly recommended to put the foam into plastic bags to prevent soil and roots from getting in between the pieces.

Note: Many companies are now turning to biodegradable foam balls such as the eco pops used by beauty company Lush. While these are great for the environment, they might not be as good as a planter filler as they’ll eventually need replacing.

2 – Household Recycling

When we say household recycling what we are actually referring to are things like plastic bottles and cans. Homes in the UK get rid of a staggering number of these and while local recycling schemes are far superior to what they were a decade ago, we don’t always have to throw things straight into the bin. Old pop bottles, empty cans of soup and beans or even things like old plastic bags can all be reused to fill up the space in a large wooden planter. If you don’t have enough household containers, it is also possible to use upside-down plastic plant pots at the bottom of the planter.

3 – Rocks and Rubble

We’ve all got rubble lying around the garden and if you haven’t, it isn’t hard to come by. While it can look unsightly, it does serve a purpose where wooden planters are concerned. You can use things like pieces of concrete, gravel, rocks and even broken bricks or roofing tiles to fill up the space. What’s great about this method is it’s almost like a game of Tetris and you can slot various bits together to get the best coverage without too much need to cover anything up.

Step 3 – Add Soil

When choosing your soil, we would always recommend going for the highest quality you can find. Potting soil is recommended as it is screened, does not contain things like seeds or weeds and is bursting with all of the essential nutrients your plants need.

Filled Wooden Planter
Filled Wooden Planter

Ordinary garden topsoil will also be fine, but it may require a bit of maintenance and weeding from time to time. Also, depending on what you are planting, you may also want to mix in some well-rotted manure or fertiliser.

Step 4 – Plant

Finally, the fun bit. With everything all set, you are ready to transplant your plants and flowers or sow your seeds ready for the growing season.

Planting in a Wooden Planter
Planting in a Wooden Planter


Wooden planters are a popular choice in gardens around the United Kingdom, but some are pretty large and filling them up with just potting soil can eat away at your bank account. But there are lots of items around your home that you can use to fill up space in your containers so if you’ve been wondering how to fill a wooden planter then all it takes is a little imagination and innovation.

How to Fill a Planter Box Infographic

Garden Doctor Tips

“We recommend using broken bricks and rubble as this is the most natural filler!”

“Ensure that the wooden planter is lined. Excess water will cause your planter to rot!”

“Remember, if you are growing root vegetables, you may not want to add as much filler under the soil!”

“If using foam balls, keep them wrapped in a carrier bag. Not only will this prevent the roots from growing through them, but it is also far easier to clean them up if necessary later on!”

Frequently Asked Questions

What is the best thing to line a planter box with?

The best thing to line a planter box with is plastic. Plastic doesn’t break down in the soil, so it will never need to be replaced. It’s also lightweight and easy to handle, which makes it perfect for lining planter boxes that are made of wood.

What do you Line the bottom of the planter with?

I usually line the bottom of my wooden planters with a layer of heavy-duty plastic. This helps to prevent the wood from rotting and also makes it easier to clean the planter when needed.

Will a wood planter box rot?

Yes, a wood planter box will rot over time if not treated or lined with plastic. One factor in determining how long your planter box will last is the type of wood that you use. Cedar and redwood are both naturally resistant to rot so using one of these woods is a good option.


Trevor Wright is not just a seasoned horticulturist; he’s the esteemed Garden Doctor. With a BSc in Horticulture and years of hands-on experience in the soil, Trevor has become a trusted mentor for all things gardening. As the founder of Garden Doctor, he’s committed to clarifying the intricacies of gardening, offering straightforward advice that’s rooted in years of practice. His writing is a garden of how-tos, savvy insights, and comprehensive guides that enable individuals to nurture and grow their garden dreams. When he’s not knee-deep in garden beds, Trevor is at his keyboard passing on his green-thumbed wisdom to budding gardeners, ensuring that the legacy of sustainable and joyful gardening blossoms far and wide.

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