What to put on the bottom of a raised garden bed?

I will jump right in and give you two answers to what you should put at the bottom of your raised garden bed.

You should place a layer or garden fabric, cardboard or newspaper to prevent weeds from growing. And on top of this layer you can place branches, scrap boards and planks and pretty much any other woody and organic material you have laying around. Here we explain how to use your garden "refuse".

Read on and I will explain why we always build new – or rejuvenate existing – raised garden beds when we prepare our garden for winter.

This article will first show you how to build a raised garden bed.

I will also list the 3 types of raised garden beds and explain why we build bordered and raised garden beds in containers.

The article will be rounded off by discussing some of the advantages and disadvantages of raised garden beds.

Build raised garden beds as we put our garden to bed

Every fall we spend time preparing our garden for winter. Getting everything sorted before winter gives us a welcome head start when it is time to plant leafy greens as early as January the following year.

The process of putting our garden to bed always creates a lot of branches and other organic plant matter as sour cherry trees, plants, and bushes are cut back.

Some of the garden "waste", branches and compost that will fill my new raised garden beds
A good clean-up gave me a lot of materials to use for my new raised garden beds

Instead of renting a trailer and driving to the local recycling center, we have learned to use this organic matter as food and nutrition for our harvests to come.

Now, it does take time for logs and even branches to decompose into compost. But we have time. We just make sure to use it as a base or foundation for our raised garden beds. 

There are several advantages to using logs, branches, and other plant matter as a foundation for your raised garden bed.

  • save money on renting a trailer or at least driving to the recycling center
  • spend less money on the soil to fill your raised garden bed
  • as the matter decomposes it will provide moisture and nutrition to your soil
  • it feels great when your garden manages to create a circle of life pattern
I recommend using borders or dig down below ground when you use logs, branches, etc, as a foundation for your raised garden bed. You can build raised garden beds with sloped sides but it makes it a lot more complicated to create a structure that will cover the material. 

8 Steps to build a raised garden bed at home

It is not difficult to build a raised garden bed. Here are the 8 steps to build your very own bordered raised garden bed.

  1. Locate a good place for your raised garden bed
  2. Decide the size you need
  3. Prepare the location
  4. Place weed blocking layer
  5. Position borders around the sides
  6. Complete the foundation
  7. Fill up the raised garden bed
  8. Cover bed with mulch

Now, let us look at each step in more detail as we build our raised garden bed.

1. Locate a good place for your raised garden bed

From my experience raised garden beds are rather permanent fixtures when they are built. They can of course be moved but it is not a fun or easy process.

Questions you should ask yourself are:

  • will the location suit the herbs or vegetables you are planning to grow? Enough sun? Too hot? Windy?
  • does the location make sense for you and your family? It may be a perfect location for growing beefsteak tomatoes but does it fit with your outdoor garden lifestyle?

2. Decide the size you need

Bigger is not always better as you need to have easy access to the entire grow bed area. 

The length of your garden bed is of course only determined by the space you have available.

Deciding on space and location for raised garden bed
Deciding the location and size of raised garden bed

But the width does come into play as you should be able to reach all areas without stepping on and compacting the soil. With bordered garden beds you can place planks across the area to create a bridge for access. But do you really want to balance on your knees while gardening?

Also, always remember that you do have to fill the whole garden bed with soil and organic materials. 

When you decide on the size of your raised garden bed you need to consider aspects like:

  • will you have access to the raised garden bed from one or two sides? 
  • can you reach the whole grow area comfortably?

3. Prepare the location

Mark out the area and clear it from debris, weeds, and other unwanted material. 

I always dig down about 10 centimeters (4 inches) but you can of course build up from ground level as well.

Digging down loosens the soil and allows me to bury the branches and other organic material below the ground. 

When the area is clear and dug out I spend a few minutes making sure the edges are reasonably straight for my borders.

4. Place weed blocking layer

Place garden fabric, newspaper, or cardboard at the bottom of your raised garden bed. Again, this is optional but if you do create a layer to block weeds it must be porous to let water drain off.

Do not use plastic or any other material that will hurt drainage. 

Make sure that the weed blocking layer is large enough to cover the sides of the dug-out area. This way your borders will rest on the layer and create a snug fit.

5. Position borders around the sides

I am a firm believer in using what you have. But I also try to make it visually pleasing. 

For me, this means no plastic. But you can of course use a plastic border if you want.

You can of course build raised garden beds with sloped sides and avoid using borders altogether. I know some gardeners find this more visually pleasing. I do prefer using borders as it provides a firm structure and holds everything in place.  

When you build the borders you can for example use stones, planks of wood, or bricks.

Today, I am using planks of wood as I already have them and I think it looks nice.

6. Complete the foundation

Place the logs, branches, etc. on top of the weed-blocking area at the bottom of your hole. Try to cut down the pieces to a size that creates a somewhat flat and even layer. 

When I am pleased with the level I use compost or grass clippings and other semi-composted materials to create a thin layer on top. This will help the process get started.

7. Fill up the raised garden bed

I use a mixture of roughly 60% top or garden soil and 40% compost to fill up my raised garden bed to the desired level. 

Good drainage is vital. Do not compact your soil, rather use a pitch to loosen it. If the soil is too compact and water does not drain well you can add and mix in coarse sand, organic matter or perlite if at hand.

Three out of four raised garden beds in place
Garden beds coming along nicely

The needed depth of the grow bed depends on what you intend to grow. For shallow-rooted herbs and vegetables like basil and lettuce a depth of 20-25 cm (8-10 inches) is sufficient.

I tend to aim for a depth of 30-45 cm (12-18 inches) of soil when I build my raised garden beds. This allows me to grow most non-root vegetables.

But if you for example are planning to grow carrots or beets you should add another 10cm (4 inches) or so of depth. 

8. Cover bed with mulch

When the raised garden bed has been filled you should pat yourself on the back. 

Now cover the surface with mulch (or cardboard) to keep weeds in check and then wait for spring to arrive.

The soil will compact over time. Come spring you may need to top up the level of the soil. Let time work for you. There is no need to walk all over the garden bed to compress the soil.

You want the soil structure to be loose and full of air.  

The foundation of logs, branches, and other organic matter will decompose over time and you have many years of great harvests ahead of you.

Rejuvenating existing raised garden beds

If you already have raised grow beds you can use the exact same method to rejuvenate your soil.

Over time the soil in your grow beds will get more and more compact and dense. 

Most of the time we only work with the top layer as we plant, weed and look after our herbs and vegetables.

Grab a spade and start emptying the soil onto a large piece of tarpaulin or something similar. 

When you reach the bottom you can place your branches and other materials in the bottom before you start filling up the garden bed again. 

This is also a perfect time to improve the quality of your soil. You can for example mix in coarse sand if your soil is too dense and compact.

Just the simple fact that you dig out and then refill your raised garden bed will help aerate your soil and create a better growing environment for your plants for the coming growing season.

And again, it is a great feeling to create a cycle of composting in your very own garden.

Types of raised garden beds

There are three main types of raised garden beds and we use two of the three in our gardens.

Raised garden beds with borders

Most of our raised garden beds are built with borders. And there are several advantages to bordered garden beds.

The border creates a structure to hold the soil and can also be used to support stakes or other support structures as needed.

Another advantage is also that the border does create some level of protection against unwelcome animals and pests. 

Finally, the border does help to retain moisture better than a completely unprotected raised garden bed.

The only disadvantage is that you do have to create the border and it could involve spending money on materials.

Raised garden beds with sloped sides

Garden beds with sloped sides are easy to build. They are also the least expensive of the three different types of raised garden beds.

The main reasons we do not use garden beds without borders are 

  • give less growing area as the sides are sloped
  • completely exposed to the elements and dry out quicker
  • harder to work with as the soil is not held in place by a structure

It is not difficult to construct a border and you do not have to use expensive or even store-bought materials. Use what you have – borders will make your gardening life easier.

Raised garden beds in containers

Raised garden beds built like containers are pleasing to the eye and very easy to work with.

The firm container structure allows for easy covering with plastic fabric or glass panels when and if needed.

The container itself helps retain soil moisture and requires less frequent watering compared to the other types of raised garden beds.

As the container sits on the ground the containers are also “less work to move”. I am not saying they are easy to move as they tend to be very heavy.

The two main downsides are however that they are more expensive to build and it does take time and effort to build them. 

We only have 6 raised garden beds in containers and they have all been built from material left over from other projects. 

Four of the container raised beds are square and quite deep measuring 56 cm x 56 cm x 56 cm (22 x 22 x 22 inches). Here we grow vegetables like chilies and tomatoes.

The other two are rectangular with a depth of 40 cm (16 inches) measuring 160 cm 90 cm (63 x 35 inches). Here we grow herbs, lettuce, and other leafy garden vegetables as well as most other non-root type vegetables.

Summary and conclusion:

If you have the space, raised garden beds offer several possibilities and advantages to a garden. But there are also a few factors that you should be aware of before you start building your very own raised garden beds.

Before I list the advantages and disadvantages I want to stress the importance of using well-drained soil.

And what I have personally found is that it makes it easier to manage the soil quality when using a raised garden bed. As the space in each garden bed is smaller and defined I have found it helpful to attack one raised garden bed at a time. And working on a rolling schedule has helped me to over time have a better growing environment for our herbs and vegetables across all our garden beds.

The main advantages are:

  • As the garden beds are raised the soil warms up more quickly in the spring
  • Raised garden beds also hold warmth longer giving you a longer growing season
  • Allows you to control drainage and improve the soil as needed (add sand, peat moss, etc.) 
  • Improved drainage and looser soil structure as no foot traffic on grow bed
  • Allow you to use organic matter like logs, and branches for your very own composing cycle
  • More comfortable working position than a traditional ground-level vegetable garden

Disadvantages include:

  • it does take time and money to build a raised garden bed
  • as garden beds are raised they are prone to dry out quicker if the weather is hot and dry
  • raised garden beds are, based on my experience, permanent fixtures when they are built
Tomatoes grow well in a raised garden bed
Helpful sources:
University of Maryland, College of Agriculture and Natural Resources

Texas A&M AgriLife Extension (Priscilla Files, Michael Arnold, Douglas Welsh, and Frank Dainello)

Meet the author: Mattias is an experienced gardener spending most of his free time on his knees among herbs, plants, and garden vegetables. For the past two years, he has been sharing gardening projects and how-to tutorials on the NordicLavender website and YouTube channel.