How to Build a Raised Garden Box

This little corner of my garden has never grown anything well. You can see that even the crazy vining watermelon are going around this little patch. My garden is mostly raised beds anyway, so this looks like the best spot for the next one.

I want a three foot aisle between the existing raised bed and the new one, so I'll start by marking the first corner away from the old bed.

The new bed is going to be 4 feet by 4 feet, just like the old ones, so I measured 3 feet from the two corners. If you happen to blast your tape measure with the marking paint, a little WD-40 and a shop rag will get it off, if you do it right away. I keep them handy when I'm marking.

Now I'm measuring straight back four feet from the mark.

Last corner.

The points should be the corners of the box (roughly). I want to clear away all weeds and grasses and get a good foundation for the box, so I'll be digging all the way to the points, so I marked each corner again a few inches away from the corner.

I am going to clear away all the weeds with a mattock.

I've cut out all the weeks around the perimeter of the bed. There are still some in the middle, but I need to get some of the mass out of my way. Time to switch to a rake.

I'm pulling the weeds and vines out and exposing the ones that still have a grip.

Back to the mattock to finish off the persistent weeds.

Another pass with the rake and the site is weed free and fairly level.

I am using ACQ treated lumber, which is certified safe for human contact. I chose 2x10s. Any width will work, but in my experience, deeper is better. 2x12s are expensive, compared to other dimensions, and tend to warp more, so I settled on 2x10s. Here I'm marking with a square at 48 inches on an 8 foot 2x10.

Make the cut on the marked line. I have built many projects like this with a hand saw or hand held circular saw, so don't be discouraged if you don't have a sliding miter saw. It's a luxury, not a necessity.

Take the other piece, measure 45 inches, mark with a square and cut. The 2x10s are 1-1/2 inches thick, so with the 48 inch boards outside the 45 inch boards, the box will be 48" x 48" finished dimension.

On the 48 inch boards, measure one inch from the edge and mark a square line.

Mark at 2, 4, 6, and 8 inches on the square line.

Place a piece of scrap under the board, and another of the same thickness at the other end. Drill a 1/8" pilot hole at each mark. Repeat on the other end of the board, and both ends of the other 48" board.

Treated lumber can be brittle. Pilot holes will prevent splitting when you screw the planter together.

Here the boards are laid out in rough position.

Hold the boards so the the end of the 48" board is flush with the face of the 45" board, and the tops are flush with each other. Drive in one 3" exterior grade construction screw (they're coated for use with treated lumber). Confirm that everything is flush and drive in the remaining three screws.

Lay a level on top of one of the boards that is part of the assembled corner. Adjust it up or down by digging or filling as needed. In the photo, if you look right below the left handle of the level, you can see that I've propped the board up on a small stone to hit dead level. I'll fill in under the board later.

After leveling the first side, I can see that the next board needs fill under it to keep the tops flush. I am raking soil and gravel into a mound to support the board.

I set the board on the mound of fill and tapped it down until it was flush with the joining board. Once it is flush at the top and face drive in the screws.

Now fill or rake out as needed to level the newly added side.

Repeat the procedure for the other sides, leveling, keeping tops and faces flush and screwing the corners together.

Measuring the two diagonals will tell you if your bed is square. If the diagonals are equal, your box is square. If you made all the cuts right and put the joints together right, it should be very close to 67-7/8". If one diagonal is longer than the other, rack the box so that they're equal. If you're trying to line up with other structures, check those dimensions, too. In just a few minutes, it's going to get really hard to change things.

Now comes a ticklish question...what do you put in it? If you have to buy everything, thousands of people are successful with a blend of one third compost, one third vermiculite and one third sphagnum peat moss. This mix will need a healthy dose of fertilizer every year, but so will most things. I am using compost that I have made myself, river sand and rice hulls that were used as bedding in my chicken coop.

Here's something I have been successful with, but isn't a necessity. If you happen to have access to some really rotten wood -- like an old pile of firewood that hasn't been used and is rotting -- Scatter some in the very bottom of your raised bed. When worms and fungi start working on the wood it becomes a sponge, absorbing water when it is plentiful, and slowly releasing it when things dry out. The more rotten the better.

I am mixing each addition with the rest of the soil. The chicken litter and rice hull mixture is mixed in heavier in the upper two thirds. The lower third is the sand/compost mixture filling in around the rotten wood.

I have more or less done the filling in thirds (working toward the camera). I've got the first two thirds done, and now have my rotten wood base in the bottom of the last section. Now I'll add some compost and sand and then chicken litter and rice hulls.

I used rice hulls as a soil amendment even before I got chickens and started using it for bedding. It aerates the soil and breaks down slowly. Lace it with chicken litter and you have something very special for your garden.

Filled, mixed and raked out. Now it just needs to rest a few days, get watered a few times and get topped off with more compost after it settles. Then it will be ready to plant.