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Low Cost Solutions for Filling Your Raised Bed Garden with Soil

Timothy Boyer Ph.D.'s picture
How much dirt does it take to fill a raised garden bed?>

One of the truths of raised bed gardening is that the cost of filling your raised bed garden with soil can easily exceed the cost of buying or building the raised bed garden frame itself. Here are some low-cost solutions for filling your raised bed garden with soil, a few of which are nearly dirt cheap.


Earlier, we learned that building a startup garden can be both simple, easy and inexpensive—with a focus toward saving money. However, one factor new gardeners often do not realize until it is time to fill their raised garden bed with soil is that depending on the size of the box, it can take a lot of commercial garden soil to fill that box—and it doesn’t come cheap!

While surfing through some of my favorite gardening videos, I came across one by “Gardener Scott” on YouTube. Gardener Scott is an experienced expert on gardening who offers advice for everyone thorough videos that show how to garden, explaining why it works, and what can go wrong.

The following is a summary of one of his gardening videos with some added advice on low cost solutions for filling your raised bed garden with soil.

How to Calculate Your Soil Needed to Fill Your Raised Bed Garden

Work Out the Math: The first step is to work out the math on just how much soil is required. This is just an estimate because you can expect some settling and compacting of the soil to occur, which will lower your final depth.

When talking about soil, most commercial bags will list the amount per bag in cubic feet. A cube has the dimensions of height, width and length. A cubic foot is a cube that measures 12 inches by 12 inches by 12 inches. But to keep the math manageable let’s deal strictly in cubic feet.

Your typical raised bed garden measures 4 feet by 8 feet by 1.5 feet. Therefore, the product of the width, length and height gives us a measure of 48 cubic feet. That’s a lot of dirt.

Now, factor in the cost of a typical name-brand bag of gardening soil sold in the gardening section. Bags come in various sizes, but common are bags that contain 1.0 cubic feet of dirt. Multiply that by the cubic feet your garden requires, and it comes to 48 bags of dirt. At a price of say $4.50 per bag of name-brand quality soil, the final cost of filling your raised garden bed comes to about $216.00. That’s a lot of money. Dirt isn’t so dirt cheap…or is it?

Consider Your Options: You can knock the cost of dirt down by buying the name-brands during a sale, by opening a credit card at the store, or choosing a not-so-name-brand garden soil that sells cheaper or offers more dirt per bag. However, you will find that your cost is still at least $190.00.

One caveat that Gardener Scott offers toward buying the cheapest dirt in the gardening department that comes in generic bags labeled “Top Soil” is that often those bags come with no labeling telling you exactly what their definition of “Top Soil” is, and therefore it remains a mystery about what exactly is going into your garden. So be forewarned.

What Gardener Scott recommends is a combination of three methods that depends on how deep your garden is going to be built. A normal raised bed garden depth is 9-12 inches of soil. In some cases, a deeper box may be needed that could be up to 1 foot and a half deep.

For Raised Beds that are Shallow

For a raised garden bed that is on the lower side of depth, you can save a significant amount of money just by buying top soil in bulk from a soil supplier that delivers it by the truckload. This soil is typically a mixture of topsoil, compost and humus. The cost of filling the raised bed is somewhere between $30-$60 per 48 cubic feet of raised bed. A real savings comes in if you have multiple raised beds to build; or, split the cost with a neighbor who also needs to add topsoil to his or her garden, but does not need a truckload worth of dirt.

For Raised Beds that are Deeper

A favored method of Gardener Scott’s is what he calls the “free method,” where the lower half of your raised bed garden is filled with materials that can come at no cost.

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First choose your spot for your raised bed garden. Dig out the grass in that spot along with some if its soil and set both aside.

After digging out the grass, make sure the area is level. You will want to have a level foundation of earth to prevent rainfall from washing your garden soil from one end of its box to the other.

The next step is to fill the lower half with twigs, branches and small logs that have decayed. You can find accumulated piles of these in many yards where often someone will be grateful to have you haul the mess out from their yard.

After the refuse is placed in the bedding spot, take that grass and dirt you dug up earlier and toss it on top of the woody refuse. You can supplement the dirt with bags of lawn clippings, weeds and dead leaves and other organic refuse you may have around. The benefit of this step is that while growing your veggies, you are actually creating new healthy soil with the decomposing woody refuse. And it’s free!

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Next, augment that lower layer with one bag of commercial organic mushroom compost and one bag of peat moss to give the lower layer a good start on self-composting. Both together should come to under $10 total. However, if you have been composting in advance, then you can skip the bag of organic mushroom compost and one bag of peat moss and just add your compost to the top of the lower layer.

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Now it is time for soil for the upper layer. Aside from the cost, another problem with commercial garden soil sold in bags is that it is typically a mix of various organics like moss, tree bark, and peat, but no actual dirt from the earth. While plants will grow in this commercial garden soil, the problem is that since it is all organics, it will eventually decompose by as much as 75% and thereby lower the depth of your garden over time. This means your garden will require more bags of commercial soil, costing you more money over the years. In addition, the organic material will require added minerals to nourish it.

Just as with with the lower-depth raised bed garden, Gardener Scotts recommends completing the topmost layer with the bulk sold topsoil, which should contain some real dirt along with compost material and humus. By following the combination of these methods, you should be able to keep the cost down to $50 or less. A big savings over what would have cost up to $300 right out of your gardening department.

Note: In the video, Gardener Scott also recommends adding “Biochar” as a final addition to the top layer, but that is a topic all of its own that we will have to save for another article.

Final Thoughts

The important part of all of this is that whether you are building a shallow or deep raised bed garden (or even supplementing your regular garden) is that you can implement any of the methods described above to fit your needs without being slavish to just how much of this or that is used, and still be guaranteed of having created a good foundation for a healthy garden. And just as importantly, you will have learned how to save a significant amount of money while learning good gardening practices.

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If you have your favorite method of filling in a raised bed garden, please respond below and let us share what has worked for you.

Timothy Boyer has a Ph.D. in Molecular and Cellular Biology from the University of Arizona. For 20+ years he has been employed as a freelance health and science writer. Today, with a background in farming and an avid home gardener, Timothy continues writing about science with a focus on the connection between plant biology and gardening for healthy living. For continual updates about plants and health, you can also follow Timothy on Twitter at TimBoyerWrites.

Image Source: Courtesy of Pixabay

Reference: How to Fill a Raised Bed (And Save Money) “; Gardener Scott Video on YouTube; https://www.youtube.com/watch?v=iV4DjBZqTXQ