How to Build a Raised Bed with Grass Sod Walls

 

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Finished Raised Beds

Pictured Above: Here are our finished raised beds before planting. All together there are 7 beds, all roughly 5′ x 9′, totalling about 450 sq feet.

It’s May, and I need to overhaul a large section of the yard to make way for this year’s vegetables.  I have big plans in store for replacing the existing fence around our home.  Because of that, it was important to me that this year’s garden would allow me to work around it to start working on the fence.  Eventually, the homestead will be bordered with wonderful raised beds with rock walls.  In the meantime, this is what we did.

How to Get Rid of the Sod:

My plan was to dig up the entire East side of our yard; it’s the sunniest large area and was the best section to place most of our gardening.  However, to do this I had to somehow get rid of over 400 square feet of grass.

Many permaculturalists advocate sheet-mulching, which basically involves covering all the grass up with a weed barrier that will eventually break down, such as cardboard, newspaper, or burlap.  There are a lot of glues and other chemicals used in the manufacturing of cardboard and newspaper that I personally did not want in my garden.

Burlap sacks would have been great, but they cost money around here and take awhile to break down, so I’m skeptical that plant roots would have an easy time breaking through.

Enter the sod cutter:

Removing the Grass:

Sod Cutter

This is what a sod cutter looks like. The blade on the bottom left shakes forward and backward and slides underneath the grass. You can set the depth from about 1" to 2" beneath the soil.

A sod cutter is essentially the larger cheese slicer  you’ve ever seen.  You walk behind it just like a lawnmower, but instead of clipping the grass, it slides a blade under the sod.  When it’s done, you get those neat 12 or 18-inch wide strips of sod that are typically rolled out onto new lawns.

Normally I would have just used a flat shovel and spent the whole day to do this – a sod cutter definitely isn’t a mandatory tool to create a raised bed with sod walls.  However, my friend Michael called me early last week to let me know he was renting a sod cutter for another project, and that I could borrow it once he was done since there was a 4 hour minimum.  The cost to rent a sod cutter was $55 for a 4 hour period and $85 for a 24 hour period (rented during May 2011). I paid him the extra $30 overage fee since we kept it longer than 4 hours, and so it essentially cost $30 and saved me at least 3 or more hours of shovel work.  I probably wouldn’t rent one of these again unless I was removing 500 sq feet or more of sod.  Anything less is doable in an afternoon by a couple people.

Cutting the Bed & Building the Walls:

Cutting up a total of about 450 square feet took less than 1 hour with the sod cutter.

The next step was to use the cut strips of sod to build the walls for our raised beds.  Here’s a rough outline of how the grass was used:

Sod Walls Raised Beds Diagram

The strips of sod in blue were flipped over in place to form the walls of the raised bed. The remaining strips were moved on top of the blue areas (grass facing down) to build up the sod wall. The white lines are roughly 12 inches apart.

Building the walls actually took longer than cutting the sod did.  There were 2 of us moving the sod strips into place and it probably took 45 minutes.  Cutting the sod took maybe 30 minutes after we got the machine running.

Pulling Back the Strips of Sod

Pulling Back the Strips of Sod

After the sod walls were built up, here’s what they looked like:

Raised Beds with No Fill

Raised beds with no fill yet, just walls. The black thing in the middle is our composter, which had to be moved at one point, so we set it down inside the bed.

Filling the Beds with Compost, Wood Chips, and Soil

The next step is the start filling up the bed with compost & soil.  I prefer to use what’s on location as much as possible, so I layered a ton of grass clippings, then sticks and twigs and branches from our yard to fill up the bottom layer. From there, I dumped about 6 yards of poplar wood chips in the beds about 16 inches high. On top of that I dumped about 6 inches of soil.

I did end up having 10 cubic yards of “veggie mix” soil delivered.  It would be nice to build all of our soil from onsite and improve it up over the years, but this is one area where I need a quick infusion of nutrients.  It will likely be the last time I need garden soil brought in, so it’s a worthwhile expense to me.  The total cost of the soil was $367 including tax. A small price to pay for awesome veggies, I suppose.

Hugelkultur

At this point, I’m sure a few people will point out that all of those wood chips have huge carbon levels and will lock up all the nitrogen in the soil.  These beds are a form of hugelkultur (proper hugelkultur would use more stumps than wood chips, but they have a similar effect).  The first couple years there is a chance that nitrogen will get sucked up by the wood chips.  Compost, grass clippings, and a few other nitrogen sources on top of my heavy feeding crops should help to mitigate this.  Eventually, the wood will have soaked up so much nitrogen that it begins releasing that nitrogen.  So there’s a long term payoff that I think can be reduced in the early years.

In the meantime, that wood soaks up huge amounts of water, which is in turn soaked up by my veggies.  That’s important here in Seattle, where we have very dry summers.  This first summer, I’ll still have to water regularly, since the wood chips haven’t had enough rain to soak up.  In year 2 I will theoretically need to water far less than a traditional raised bed without all of the rotting wood inside.

Poplar Wood Chips

Poplar Wood Chips - I hauled 3 truckloads of this from some freshly cut poplar trees not far from here. In total there was about 6 yards of these wood chips

10 Cubic Yard of Soil

This is what 10 cubic yards of soil looks like. This is a veggie mix consisting of 50% top soil, 25% Cedar Grove compost, and 25% organic "moo doo," aka aged cow poop. To give you some perspective, that wheelbarrow is much bigger than most (and it's a 2 wheeler), and it's sitting uphill from the dirt pile.

Mounded Raised Beds

Here you can see that there are 6 wide mounds forming the raised beds. All of the mounds are 10 feet long, and they're all 4 to 6 feet wide. Additionally, beyond the fence there is a 7th raised bed by the driveway, where we get our maximum sun. The space in between the mounds will be sunken pathways.

Raised Beds in Mounds

Here you can see some of the layering of the beds. Out of sight at the bottom there are grass clippings and tons of branches. On top of the branches we poured about 16 inches of wood chips to form mounds. On top of that we dumped some coffee grounds and grass clippings, and then we topped that with finished soil.

Raised Bed Drainage Trench

I observed after building the walls of the raised bed that rainwater was accumulating on the uphill / West side of the raised beds. So I dug a trench underneath the pathways. Now the water will follow the blue arrows when it rains, and soak into the soil underneath the beds where the plants can access it. The trench and pathways will have wood chips filled in, which I don't believe will affect the drainage trench significantly.

Raised Beds Before Planting

This shot shows 6 of the 7 raised beds after all layers of wood chips & compost & soil have been added. You can see they are substantially higher than the pathways alongside them, roughly 24 inches I think.

Add Some Finishing Touches

Pole Bean Teepee

I lashed up a quick pole bean teepee last night and planted some pole beans at the base of it, along with some mycorrhizal inoculant. This tee pee is roughly 10 feet tall at the connection point. Obviously we won't be harvesting everything at the top, but we should be able to harvest most of the dried-out beans when we take the teepee down at the end of the growing season.

Finish With a Living Mulch

Raised beds can be notorious for drying out quickly, because the water tends to obey gravity.  As a result, it is super important to have some sort of mulch to help the beds retain whatever moisture they have. I have decided to use a “living mulch”, which is just a mulch made out of a cover crop of some sort.  In this case, we will seed the walls of the raised beds with New Zealand White Clover. This will act as a living mulch by preventing weeds from forming on the wall and retaining moisture, but it will also attract bees and fix nitrogen into the soil, not too mention look good.  For more information see my post about clover as a living mulch.

Broadcast White Clover Seed

Broadcast White Clover Seed - Note - if you broadcast seed like this, be certain to cover it with 1/8 of an inch of soil if you want it to sprout properly. I noticed that the only seeds sprouting for us were the ones that fell in cracks (where they didn't dry out so fast).

Total Cost

My grass clippings, branches, sod and wood chips were free.  I spent $8 on a pound of clover seed and used about 60% of it.  I spent $30 on the sod cutter.  This could have been free with a shovel and a couple friends.  I spent $34 per yard on the veggie mix soil.  I probably used 2 or 3 yards for the garden beds, so let’s say $90 on soil.  This also could have been free if I had just used soil on hand.  While my total cost was $130, it’s important to note that $120 was spent on shortcuts.  The primary cost of building these beds is a little sweat and finding the materials.  So these raised beds can work for any budget.  Also, had I not raised them so high, I would have needed less material, which would have made the beds much closer to free.

So, that’s how we built our raised beds.  They are still an experiment in progress, so be sure to follow along with us for the growing season to see how they turn out and too see what we would have done differently.

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This post was written by Kane

Kane lives on the Seattle Homestead in West Seattle. Lately he's spent most of his free time finishing up the homestead wall project and getting ready for planting the new garden beds. Kane is also the founder of Content Harmony, a content marketing agency based in Seattle.

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