Start a Garden Week 2: Building the Raised Bed and Adding the Soil Mix

published Apr 8, 2014
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(Image credit: Regina Yunghans)

Last week I showed you my plans for a raised-bed garden. This week, let’s talk about how we built the beds.

When we demolished a rotting deck off of the rear of our home two years ago, there were two cedar beams used as railings. Even then, we knew we wanted to use the 4x8x12-foot-long beams to build a raised bed planter, so we stored them away and saved them for a season when we had time to finally get around to planting a garden: This is the year!


We used cedar because we didn’t want the chemicals from treated lumber to be anywhere near our food. These cedar beams are old and weathered, but have proven themselves through the test of time. Their hefty dimensions will make them a comfortable place to perch when gardening and they allow for an 8-inch soil depth.

We simply cut four feet off of each beam to be used as the 4-foot sides and used the remainders as the long sides of the bed. Drilling deep pockets into the wood, we screwed the pieces directly to each other with long stainless steel screws (oils in the cedar will react with galvanized screws and cause corrosion).

(Image credit: Regina Yunghans)

The Soil Mix

With the bed in place, we were ready for the soil mix. We took one weekend to gather all of the components for rich soil, as our local earth is full of clay and not good for gardening. Loosely following the “recipe” for Mel’s Mix (the soil recommended by Square Foot Gardener Mel Bartholomew), we set out to gather 1/3 proportion coarse vermiculite, 1/3 peat moss, and 1/3 compost in a quantity of about 18 cubic feet. Here’s what we ended up with:

  • Coarse vermiculite: This can be purchased in large 4 cubic foot bags. It’s pricey, but will hold up year after year so it doesn’t need to be replenished every season.
  • Cotton Burr Compost: Per the recommendation of a local nursery, we used this in place of much of the peat moss. Peat moss use is depleting natural peat bog wetlands and there are several alternatives that do the same thing as peat moss without causing as much environmental harm. We chose cotton burr compost, but always consider your source. Here’s what we used: Back to Nature
  • Compost: Bartholomew recommends a mix of different composts to provide a wide range of nutrients to your soil. We used several that were easily accessed in our locale: cow manure compost, poultry manure compost, mushroom compost, and earthworm castings.

Mel’s Mix can also be purchased online from Home Depot, but shipping costs can be prohibitive. They were for us, so we gathered the materials ourselves. If you were doing a small container or a single square foot, it would likely be best to buy the premixed soil to incorporate all of the ingredients at a small quantity.

To mix the soil, we laid a large tarp out on the ground next to the raised bed. After dumping each component on the tarp, it simply took mixing and stirring thoroughly with shovels and then moving the mix by wheelbarrow-full into the bed. Before filling the bed, we tilled the ground in the bottom of the box to break up the earth and allow roots to penetrate the earth if they need to, essentially providing a little more depth to the bed.

Finally, a square foot grid was laid out across the garden using twine pulled taut and stapled to the frame. This will provide a guide when it comes time for planting.

What’s Next?

Our sprouts are coming along nicely and we plan to get them into the ground in May. Before then, we’ll be planting some crops from seed in the coming week or so, which we can’t wait to share with you next time. Also, look for an upcoming post on trellising and staking.