I have built many raised garden beds over the years, and the method I use is easy-to-follow, economical, and creates a growing environment that will yield excellent results for years to come.
This guide consists of 3 parts:
- Explaining the NordicLavender method of thinking in thirds
- Questions to consider before you start building.
- Step-by-step instructions on how to build a raised garden bed
Building a raised garden bed is simple, but it can be back-breaking work as it involves digging, shoveling soil, and working with wood. It is not hard work, but it qualifies as a good workout.
- 1. Locate a good place for your raised garden bed
- 2. Decide what size you need
- 3. Prepare the location
- 4. Place weed blocking layer
- 5. Position borders around the sides
- 6. Fill the bottom third of the raised garden bed
- 7. Fill up the second third of the raised garden bed
- 8. Fill up the final third of the raised garden bed
- 9. Cover the bed with mulch
1. Building a raised garden bed in thirds
I always plan my raised garden beds in thirds. It saves a lot of money, makes good use of garden waste, and yields excellent results over many years.
1. The bottom third
The bottom layer is essential, but for now, this layer is all about using good organic matter and material to fill the garden bed inexpensively.
Using logs, larger stems, dry firewood, and branches also helps the soil retain moisture while aerating the soil.
This layer will decompose and add goodness to our raised garden bed over time, but it is a filler for now.
2. The middle third
This middle third is closer to the growing area, and we use a reasonably fertile mixture of lower-quality garden soil (60) and compost (40).
We would never use this 60/40 mixture to grow vegetables. But here, in the middle, it will fill up the garden bed, add some nutrition, and, more importantly, provide good soil structure, aeration, and drainage.
3. The top third – our grow bed
This top layer is where we will plant and grow vegetables and herbs this season.
Here we go full out and use the best quality potting soil and compost mix we can.
But remember, more compost is not necessarily better. You want well-balanced, fertile, and well-draining soil to help your plants grow strong and healthy.
You want this top layer to be a minimum of 15-20 cm (6-8 inches) deep to promote healthy root systems and vigorous plants.
2. Questions to consider before you start building
Before considering the location and what to grow, consider the following factors.
Height of garden bed – comfort and access
Raised garden beds are great for gardeners suffering from an aching back or sore knees or generally prefer a more upright and comfortable position when gardening.
If you want a comfortable gardening position, consider building a raised garden bed with borders at least 50 cm (20 inches) above ground level.
But remember that height can work against you if you are, for example, planning to grow pole beans or indeterminate tomato varieties like beefsteaks.
Get materials and fillers before you start building
The method of thirds will help to keep costs down, as filling a raised garden bed from top to bottom with top-quality soil would be too expensive. And frankly speaking, unnecessary.
Still, plan and ensure you have enough materials and fillers to complete your project before you start. As we are using garden waste, most people are happy to give you theirs.
3. Step-by-step instructions on how to build a raised garden bed
It is easy to build a raised garden bed. Here are the 9 steps to make your bordered raised garden bed.
- Locate a good location for your raised garden bed
- Decide the size you need
- Prepare the location
- Place weed-blocking layer
- Position borders around the sides
- Fill the bottom third of the raised garden bed
- Fill the second or middle third of the raised garden bed
- Create your grow bed in the top third
- Cover the 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
Raised garden beds are somewhat permanent fixtures when built. You can move them, but it is a challenging 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 your outdoor garden lifestyle?
- Do you have easy access to a water source, or will you carry watering cans all summer?
- What used to grow in the area where you plan to build your raised garden bed? Lots of weeds? Has the site been exposed to pesticides or other non-organic chemicals?
You should use a weed-blocking layer if the area was covered with weeds before.
Consider choosing a closed-bottom raised garden bed if the ground has been exposed to pesticides or non-organic chemicals.
2. Decide what size you need
Bigger is not always better, as you need easy access to the entire garden bed area.
The available space will determine the length of your 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 want to balance on your knees while gardening?
Also, always remember that you must fill the whole garden bed with soil and organic materials.
When you have decided on the size of your raised garden bed you want, 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?
- And if you can only get halfway, will you be happy switching sides every time you garden?
3. Prepare the location
Mark out the area and clear it of debris, weeds, and other unwanted material.
I always dig down at least 10 centimeters (4 inches), but you can build up from ground level as well.
Digging down loosens the soil and allows me to bury the branches and other organic material below ground level.
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 cardboard, garden fabric, or newspaper at the bottom of your raised garden bed. Again, this is optional, but if you create a weed-blocking layer, ensure it is porous to let water drain.
Do not use plastic or any other material that will hurt drainage.
Ensure 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 build raised garden beds with sloped sides and avoid using borders altogether. Some gardeners find this more visually pleasing. I prefer using borders as it provides a firm structure and holds everything in place.
When you build the borders, you can also use stones, planks of wood, or bricks.
Today, I am using wood planks as I already have them, and I think they look nice.
6. Fill the bottom third of the raised garden bed
Place the logs, thick stems, branches, etc., on top of the weed-blocking layer at the bottom of your hole. Cut down the pieces to a size that creates a flat and even layer.
When I am pleased with the level, I add compost, grass clippings, and other semi-composted materials to create a thin layer to help start the decomposition process.
7. Fill up the second third of the raised garden bed
This second or middle layer is more about retaining soil moisture, providing soil structure, and excellent drainage than outright nutrition.
This layer is closer to the growing area, and we use a reasonably fertile mixture of lower-quality garden soil and compost.
The vegetables we grow this season will not reach this layer. But it will decompose further and, over time, become an essential part of the growing environment.
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.
You can use garden soil from your actual garden or buy it in bulk from a supplier. You do not need top-quality soil for this layer.
We would never use this 60/40 mixture to grow vegetables. But here in the middle, it will fill up the garden bed, add some nutrition but, more importantly, provide good soil structure, aeration, and drainage.
As for the compost, use partly decomposed grass clippings, leaves, and other garden waste but avoid fresh green clippings and trimmings. You want the compost to be more brown than green.
Good drainage is vital. Do not compact your soil; use a pitchfork to loosen it. If the soil is too compact and water does not drain well, you can mix in coarse sand, organic matter, or perlite.
8. Fill up the final third of the raised garden bed
The next growing season comes down to this final layer of soil.
Here we spare no expense and use the best quality well-draining potting soil we have. Add up to 25% finished or mature compost, depending on the amount already added to your soil.
If you add compost, ensure it is dark, loose, crumbly, and smells like fresh soil.
The needed depth of this top layer 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 like to aim for a depth of 30-45 cm (12-18 inches) of good quality soil when I build my raised garden beds, as it 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.
9. Cover the bed with mulch
When you have filled the entire raised garden bed, you should pat yourself on the back.
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 soil level. 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 plentiful harvests ahead of you.
Rejuvenating existing raised garden beds
If you already have raised grow beds, you can use the same method to rejuvenate your soil.
Over time the soil in your grow beds will get more compact and dense.
We mostly 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 canvas or something similar.
When you reach the bottom, you can place your branches and other materials in the bottom before 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 improve the 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 garden.
Digging up and rejuvenating garden beds is somewhat controversial in the gardening community. Some feel that this never happens in nature, so why should we do it? I find it helps, but I leave it up to you to find your path.
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 own raised garden beds.
Before I list the advantages and disadvantages, I want to stress the importance of using well-drained soil.
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
- 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
I find that raised garden beds make it easier to manage soil quality. As the space in each garden bed is smaller and more 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, create a better-growing environment for our herbs and vegetables across all our garden beds.