How to Cheaply Fill a Raised Garden Bed

Hi all! Welcome back to my continuing saga on building elevated garden beds! I’m now going to talk about how you can fill your raised beds on the cheap. Although there are a lot of advantages to building elevated beds, there’s one downside – and that’s the fact that you are going to have to accumulate a fair amount of materials – and that includes soil. And though you are going to need soil which I understand is not cheap (just like everything nowadays, am I right?) there are some good and legit ways to cut costs.

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filling beds

We have begun to process of replenishing our beds (and started planting too) as when time goes by, the soil will “settle” as the lingering dead plants break down and decompose. So this year we will not need to buy nearly as many bags of dirt, but if you’re at the stage of starting out, I’d like to pass on what we know. John and I have done a good bit of price-comparisons, and to boot sometimes supplies of soil can run out, too, as everyone is getting started doing what we’re doing, after all, it’s spring!

But First: How Much Soil Do You Need?

That will depend on the size of your beds, obviously. Ours are 22 ft in length, 8″ deep and 52″ wide. Go by feet when you measure your beds to calculate cubic feet. You can look up “soil calculators” which may save time. If you apply the process I talk about here you will probably need half of the amount of soil it will tell you.

As we’ve been “topping up” our beds lately, it’s taken at least 30 bags, factor in those measurements above and you’ll get an idea.

getting bags of soil
Yes, 35 bags of soil really did fit in that hatchback…

Step 1: Begin with a layer of cardboard

Cardboard, breaks down easily, is biodegradable, and easy to obtain. Especially if you do enough online shopping. I’m always saving our boxes we get from packaging as it comes in handy for this. This layer of cardboard will stifle any weed and undesired grass growth.

As moisture develops, it will naturally break down on its own.

Layer 2 – Build out logs

Wherever you can obtain decomposing logs from the stump dump, you’re golden. Old wood that is breaking down naturally will provide a moisture retainer and producer of organic material as they break down.One thing to point out, though, be sure the wood you use does not come from allelopathic trees as these could inhibit plant growth.

There is a take on this called the “core” approach, and involves digging a 10″ trench in the middle of the bed and placing the logs in it. That’s some extra work involved, if you don’t feel like digging, try to be sure your log layer is half or a little less than that of the entire bed depth. Fill in the smaller areas with broken limbs and sticks where applicable.

Layer 3 – Accumulated Yard Waste

Another way nature helps us out, is the presence of naturally occurring materials we accumulate when mowing the lawn, raking leaves or do other cutting and trimming chores. Anything in the neighborhood of dried leaves, straw, hay, grass clippings, and the like can serve as the next layer (Over here, we have lots of pine needles and sweetgum balls – they seem to be everywhere you can shake a stick at.)

Take a look around your yard and see what you can come up with. Place this over the logs and make it about 20% of the bed’s depth.

Layer 4 – Compost

Actual composted material will be a boon for your beds, adding friendly microbes, maintaining soil fertility and preventing erosion just to name a few benefits. There’s many more, like retaining moisture and a good Ph level, too – no downsides whether you’re building raised beds or doing the traditional approach. Try to shoot for a 20% amount.

Topsoil


And finally, the fifth layer will be the soil. Topsoil bought in bulk may net you a better deal than that bought in bags. You may have to do a little research on what you can find in your area.

topsoil bags
I want to stress, though…topsoil, not potting soil, the latter is more suited to container gardening and indoor potted plants. If you do use potting soil, it needs to be a minimal amount. It’s not easy to make the distinction right away but potting soil, when you study it close up, it’s much less dense, may contain fillers like perlite, bark, and has been sterilized to some degree so it can be used indoors safely.

Sterilized soil may not have as much bioavailability when it comes to maintaining good bacteria and microbes in your outdoor garden

Wrap-Up

The biggest takeaway here, is out of this list, you can find a way to cut costs and make use of organic materials to supplement the high cost of soil, and have garden beds that thrive.

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